Preoperative immune checkpoint inhibition and cryoablation in early-stage breast cancer

Local cryoablation can engender systemic immune activation/anticancer responses in tumors otherwise resistant to immune checkpoint blockade (ICB). We evaluated the safety/tolerability of preoperative cryoablation plus ipilimumab and nivolumab in 5 early-stage/resectable breast cancers. The primary endpoint was met when all 5 patients underwent standard-of-care primary breast surgery undelayedly. Three patients developed transient hyperthyroidism; one developed grade 4 liver toxicity (resolved with supportive management). We compared this strategy with cryoablation and/or ipilimumab. Dual ICB plus cryoablation induced higher expression of T cell activation markers and serum Th1 cytokines and reduced immunosuppressive serum CD4+PD-1hi T cells, improving effector-to-suppressor T cell ratio. After dual ICB and before cryoablation, T cell receptor sequencing of 4 patients showed increased T cell clonality. In this small subset of patients, we provide preliminary evidence that preoperative cryoablation plus ipilimumab and nivolumab is feasible, inducing systemic adaptive immune activation potentially more robust than cryoablation with/without ipilimumab.

Genomic and epigenomic basis of breast invasive lobular carcinomas lacking CDH1 genetic alterations

CDH1 (E-cadherin) bi-allelic inactivation is the hallmark alteration of breast invasive lobular carcinoma (ILC), resulting in its discohesive phenotype. A subset of ILCs, however, lack CDH1 genetic/epigenetic inactivation, and their genetic underpinning is unknown. Through clinical targeted sequencing data reanalysis of 364 primary ILCs, we identified 25 ILCs lacking CDH1 bi-allelic genetic alterations. CDH1 promoter methylation was frequent (63%) in these cases. Targeted sequencing reanalysis revealed 3 ILCs harboring AXIN2 deleterious fusions (n = 2) or loss-of-function mutation (n = 1). Whole-genome sequencing of 3 cases lacking bi-allelic CDH1 genetic/epigenetic inactivation confirmed the AXIN2 mutation and no other cell-cell adhesion genetic alterations but revealed a new CTNND1 (p120) deleterious fusion. AXIN2 knock-out in MCF7 cells resulted in lobular-like features, including increased cellular migration and resistance to anoikis. Taken together, ILCs lacking CDH1 genetic/epigenetic alterations are driven by inactivating alterations in other cell adhesion genes (CTNND1 or AXIN2), endorsing a convergent phenotype in ILC.

Nonlobular Invasive Breast Carcinomas with Biallelic Pathogenic CDH1 Somatic Alterations: A Histologic, Immunophenotypic, and Genomic Characterization

CDH1 encodes for E-cadherin, and its loss of function is the hallmark of invasive lobular carcinoma (ILC). Albeit vanishingly rare, biallelic CDH1 alterations may be found in nonlobular breast carcinomas (NL-BCs). We sought to determine the clinicopathologic characteristics and repertoire of genetic alterations of NL-BCs harboring CDH1 biallelic genetic alterations. Analysis of 5842 breast cancers (BCs) subjected to clinical tumor-normal sequencing with an FDA-cleared multigene panel was conducted to identify BCs with biallelic CDH1 pathogenic/likely pathogenic somatic mutations lacking lobular features. The genomic profiles of NL-BCs with CDH1 biallelic genetic alterations were compared with those of ILCs and invasive ductal carcinomas (IDCs), matched by clinicopathologic characteristics. Of the 896 CDH1-altered BCs, 889 samples were excluded based on the diagnosis of invasive mixed ductal/lobular carcinoma or ILC or the detection of monoallelic CDH1 alterations. Only 7 of the 5842 (0.11%) BCs harbored biallelic CDH1 alterations and lacked lobular features. Of these, 4/7 (57%) cases were ER-positive/HER2-negative, 1/7 (14%) was ER-positive/HER2-positive, and 2/7 (29%) were ER-negative/HER2-negative. In total, 5/7 (71%) were of Nottingham grade 2, and 2/7 (29%) were of grade 3. The NL-BCs with CDH1 biallelic genetic alterations included a mucinous carcinoma (n = 1), IDCs with focal nested growth (n = 2), IDC with solid papillary (n = 1) or apocrine (n = 2) features, and an IDC of no special type (NST; n = 1). E-cadherin expression, as detected by immunohistochemistry, was absent (3/5) or aberrant (discontinuous membranous/cytoplasmic/granular; 2/5). However, NL-BCs with CDH1 biallelic genetic alterations displayed recurrent genetic alterations, including TP53, PIK3CA (57%, 4/7; each), FGFR1, and NCOR1 (28%, 2/7, each) alterations. Compared with CDH1 wild-type IDC-NSTs, NL-BCs less frequently harbored GATA3 mutations (0% vs 47%, P = .03), but no significant differences were detected when compared with matched ILCs. Therefore, NL-BCs with CDH1 biallelic genetic alterations are vanishingly rare, predominantly comprise IDCs with special histologic features, and have genomic features akin to luminal B ER-positive BCs.

Impact of reactive changes on multigene testing: histopathologic analysis of low-grade breast cancers with high-risk 21-gene recurrence scores

PURPOSE

The 21-gene recurrence score (RS) assay predicts the recurrence risk and magnitude of chemotherapy benefit in patients with invasive breast cancer (BC). This study examined low-grade tumors yielding a high-risk RS and their outcomes.Kindly check the edit made in the article titleOk  METHODS: We compared patients with grade 1 BC and a high-risk RS to those with low-risk RS. Histologic sections were reviewed and features reported to elevate the RS were noted, mainly biopsy cavity and reactive stromal changes (BXC).

RESULTS

A total of 54 patients had high-risk RS (median RS of 28, range 26-36). On review, BXC were seen in all cases. Thirty BCs in this group also had low to negative PR. Treatment regimens included: chemoendocrine therapy (63%), endocrine therapy alone (31%) and no adjuvant therapy (6%). There were no additional breast cancer events over a median follow-up of 54.0 months (range 6.2 to 145.3). A total of 108 patients had low-risk RS (median RS of 7, range 0-9). BXC were seen in 47% of cases and none were PR negative. One patient had a recurrence at 64.8 months while the rest had no additional events over a median of 68.1 months (2.4 to 100).

CONCLUSION

We provide further evidence that reactive stromal changes and/or low-PR scores enhance the elevation of the RS. A high-RS result in low grade, PR-positive BC may not reflect actual risk and any suspected discrepancies should be discussed with the management teams. Multigene testing results should be interpreted after correlation with pathologic findings to optimize patient care.

KIT genetic alterations in breast cancer

AIMS

Activating somatic mutations or gene amplification of KIT result in constitutive activation of its receptor tyrosine kinase, which is targetable in various solid tumours. Here, we sought to investigate the presence of KIT genetic alterations in breast cancer (BC) and characterise the histological and genomic features of these tumours.

METHODS

A retrospective analysis of 5,575 BCs previously subjected to targeted sequencing using the FDA-authorised Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Targets (MSK-IMPACT) assay was performed to identify BCs with KIT alterations. A histological assessment of KIT-altered BCs was conducted, and their repertoire of genetic alterations was compared with that of BCs lacking KIT genetic alterations, matched for age, histological type, oestrogen receptor/HER2 status and sample type.

RESULTS

We identified 18 BCs (0.32%), including 9 primary and 9 metastatic BCs, with oncogenic/likely oncogenic genetic alterations affecting KIT, including activating somatic mutations (n=4) or gene amplification (n=14). All KIT-altered BCs were of high histological grade, although no distinctive histological features were observed. When compared with BCs lacking KIT genetic alterations, no distinctive genetic features were identified. In two metastatic KIT-altered BCs in which the matched primary BC had also been analysed by MSK-IMPACT, the KIT mutations were found to be restricted to the metastatic samples, suggesting that they were late events in the evolution of these cancers.

CONCLUSIONS

KIT genetic alterations are vanishingly rare in BC. KIT-altered BCs are of high grade but lack distinctive histological features. Genetic alterations in KIT might be late events in the evolution and/or progression of BC.

Nipple Lesions of the Breast: An Update on Morphologic Features, Immunohistochemical Findings and Differential Diagnosis

Because of the unique anatomic structure of the nipple, a few specific breast lesions occur only at this site. Large lactiferous sinuses may be involved by inflammatory conditions such as squamous metaplasia of lactiferous ducts and ductal ectasia or be the site of uncommon superficial epithelial neoplasms such as nipple adenoma or syringomatous tumor of the nipple. Paget disease of the nipple may be secondary to intraepidermal extension of ductal carcinoma in situ in the underlying lactiferous ducts or develop from malignant transformation of Toker cells. Invasive breast cancer may also arise primarily in the nipple. Most of these conditions present as a palpable mass and/or skin changes with or without nipple discharge. Due to the delicate location and often relatively small size of nipple lesions, biopsy specimens are often superficial and fragmented, and the interpretation is challenging. Knowledge of the morphologic and immunophenotypic features of nipple lesions is essential in making the correct diagnosis. Information on the molecular alterations underpinning nipple neoplasms is currently very limited.

Future Practices of Breast Pathology Using Digital and Computational Pathology

Pathology clinical practice has evolved by adopting technological advancements initially regarded as potentially disruptive, such as electron microscopy, immunohistochemistry, and genomic sequencing. Breast pathology has a critical role as a medical domain, where the patient's pathology diagnosis has significant implications for prognostication and treatment of diseases. The advent of digital and computational pathology has brought about significant advancements in the field, offering new possibilities for enhancing diagnostic accuracy and improving patient care. Digital slide scanning enables to conversion of glass slides into high-fidelity digital images, supporting the review of cases in a digital workflow. Digitization offers the capability to render specimen diagnoses, digital archival of patient specimens, collaboration, and telepathology. Integration of image analysis and machine learning-based systems layered atop the high-resolution digital images offers novel workflows to assist breast pathologists in their clinical, educational, and research endeavors. Decision support tools may improve the detection and classification of breast lesions and the quantification of immunohistochemical studies. Computational biomarkers may help to contribute to patient management or outcomes. Furthermore, using digital and computational pathology may increase standardization and quality assurance, especially in areas with high interobserver variability. This review explores the current landscape and possible future applications of digital and computational techniques in the field of breast pathology.

The Presence of Extensive Lymphovascular Invasion (LVI) is Associated with Higher Risk of Recurrence in Curatively Treated Breast Cancer Patients

PURPOSE/OBJECTIVE(S)

Lymphovascular invasion (LVI) is a pathological feature seen in breast cancer that may be an important step in cancer metastasis. Multiple datasets have demonstrated a correlation between LVI and local-regional recurrence (LRR). Whether the extent of LVI is an incremental determinant of LRR risk is unknown. We describe clinical outcomes in women with invasive breast cancer stratified by: 1) absence of LVI (neg), 2) LVI focal or suspicious (FS-LVI), 3) usual (non-extensive) LVI (LVI) and 4) extensive LVI (E-LVI).

MATERIALS/METHODS

Between December 2009 and August 2021, there were 8,837 patients with early-stage breast cancer (T1-2 and N0-2a) were treated with curative intent and were evaluable. Clinical-pathological details were abstracted by retrospective review. The description of LVI was abstracted from pathology reports. Recurrence and survival outcomes were compared based on the extent of LVI.

RESULTS

Of the 8837 patients studied, 5584 were neg, 461 had FS-LVI, 2315 had LVI, and 477 had E-LVI. The E-LVI cohort had baseline characteristics suggestive of higher risk such as younger median age, higher proportion of grade 3, more nodal positivity, more mastectomy (67% vs 48%), and higher use of chemotherapy compared to LVI. The cumulative incidence of LRR and DM was highest in the E-LVI group. Using LVI as the reference, the presence of E-LVI, age, tumor size, ER status, grade, mastectomy, and close/positive margins were independent variables for LRR on Cox multivariable regression (Table 1). To assess the effect with an alternate statistical method, we created propensity matched cohorts (matched for age, size, receptors, grade, surgery type, margins and chemotherapy/RT use); a statistical difference in OS was noted between groups with LVI vs E-LVI (HR 1.44 (CI 1.06-1.96, p = 0.018), but not in LRR (HR 1.31 (CI 0.87-1.97, p = 0.2) or DM (HR 1.16 (CI 0.88-1.53, p = 0.3).

CONCLUSION

Our work suggests that patients with E-LVI are at a higher risk for LRR compared to patients with usual LVI, despite maximal standard of care treatment. This is important because E-LVI can be determined from breast specimens, and may help define indications for RNI/PMRT when nodal information is not available.

Is Surgical Excision of Focal Atypical Ductal Hyperplasia Warranted? Experience at a Tertiary Care Center

BACKGROUND

The core-needle biopsy (CNB) diagnosis of atypical ductal hyperplasia (ADH) generally mandates follow-up excision, but controversy exists on whether small foci of ADH require surgical management. This study evaluated the upgrade rate at excision of focal ADH (fADH), defined as 1 focus spanning ≤ 2 mm.

METHODS

We retrospectively identified in-house CNBs with ADH as the highest-risk lesion obtained between January 2013 and December 2017. A radiologist assessed radiologic-pathologic concordance. All CNB slides were reviewed by two breast pathologists, and ADH was classified as fADH and nonfocal ADH based on extent. Only cases with follow-up excision were included. The slides of excision specimens with upgrade were reviewed.

RESULTS

The final study cohort consisted of 208 radiologic-pathologic concordant CNBs, including 98 fADH and 110 nonfocal ADH. The imaging targets were calcifications (n = 157), a mass (n = 15), nonmass enhancement (n = 27), and mass enhancement (n = 9). Excision of fADH yielded seven (7%) upgrades (5 ductal carcinoma in situ (DCIS), 2 invasive carcinoma) versus 24 (22%) upgrades (16 DCIS, 8 invasive carcinoma) at excision of nonfocal ADH (p = 0.01). Both invasive carcinomas found at excision of fADH were subcentimeter tubular carcinomas away from the biopsy site and deemed incidental.

CONCLUSIONS

Our data show a significantly lower upgrade rate at excision of focal ADH than nonfocal ADH. This information can be valuable if nonsurgical management of patients with radiologic-pathologic concordant CNB diagnosis of focal ADH is being considered.

Impact of prior systemic therapy on lymphocytic infiltration in surgically resected breast cancer brain metastases

PURPOSE

Tumor-infiltrating lymphocytes (TILs) have been positively correlated with response to systemic therapy for triple-negative and HER2 + subtypes and improved clinical outcomes in early breast cancer (BC). Less is known about TILs in metastatic sites, particularly brain metastases (BM), where unique immune regulation governs stromal composition. Reactive glial cells actively participate in cytokine-mediated T cell stimulation. The impact of prior medical therapy (chemotherapy, endocrine, and HER2-targeted therapy) on the presence of TILs and gliosis in human breast cancer brain metastases (BCBM) has not been previously reported.

METHODS

We examined prior treatment data for 133 patients who underwent craniotomy for resection of BMs from the electronic medical record. The primary endpoint was overall survival (OS) from the time of BM diagnosis. We examined the relationship between prior systemic therapy exposure and the histologic features of gliosis, necrosis, hemorrhage, and lymphocyte infiltration (LI) in BCBMs resected at subsequent craniotomy in univariate analyses.

RESULTS

Complete treatment data were available for 123 patients. BCBM LI was identified in 35 of 116 (30%) patients who had received prior systemic treatment versus 5 of 7 (71.4%) who had not {significant by Fisher's exact test p = 0.045}. There were no statistically significant relationships between prior systemic therapy and the three other histologic variables examined.

CONCLUSIONS

This observation suggests that systemic therapy may interfere with the immune response to BCBMs and cause exhaustion of anti-tumor immunity. This motivates clinical investigation of strategies to enhance LI for therapeutic benefit to improve outcomes for patients with BCBMs.

Abstract P4-02-14: Gain of HER2 Amplification in Patients with HR+/HER2- and Triple Negative Early Breast Cancer Treated with Neoadjuvant Chemotherapy

Background: Neoadjuvant chemotherapy (NAC) is standard of care for the majority of patients with clinical stage II-III triple negative breast cancer (TNBC) and is considered in high-risk patients with hormone receptor positive (HR+)/human epidermal growth factor receptor 2 (HER2) negative (-) tumors, with expected pathological complete response (pCR) rates of 40-60% and 10-12%, respectively. In HER2- patients with residual disease (RD) after NAC, there is limited data on rates of gain of HER2 amplification. The biological and clinical significance of this phenomenon is unknown and determining the best adjuvant therapy for these patients remains a challenge. We sought to determine the rate of HER2 gain in a cohort of consecutive patients with HER2- breast cancer (BC) treated with NAC.

Methods: From 01/2021 to 12/2021, we identified patients with HER2- breast cancer treated with NAC followed by surgery at our institution. Patients who received neoadjuvant endocrine therapy were excluded. The rates of pCR (ypT0/is ypN0) and HER2 status pre- and post-NAC were assessed. Estrogen receptor (ER), progesterone receptor (PR) and HER2 status on surgery specimens were internally determined for all patients using ASCO/CAP 2020 guidelines. ER-low was defined as ER expression by immunohistochemistry (IHC) 1-10%.

Results: We included 256 patients, 130 (51%) HR+/HER2- [13/130(10%) ER-low] and 126 (49%) TNBC. Median age was 48 years (range 25-82) and the majority presented with clinical T2 (57%) and N1 (59%). Of 130 patients with HR+/HER2-tumors, 120 (92%) received dose-dense (dd) doxorubicin/cyclophosphamide-paclitaxel (AC-T). Of 126 TNBC patients, 46 (37%) received ddAC followed by carboplatin in combination with paclitaxel +/- pembrolizumab. Centralized HER2 status assessment on the core biopsy was performed in 22% of samples. Overall, pCR was achieved in 40% of TNBC and 11% of HR+/HER2-. Among the 192 patients with RD, the rate of HER2 gain was 8/192 (4%), including 3% (2/76) of TNBC and 5% (6/116) of HR+/HER2- patients. 7 of the 8 patients (88%) converted from IHC 1+ or 2+ fluorescence in situ hybridization (FISH) not amplified on core biopsy to IHC 2+ FISH amplified on the surgical specimen. In only 1 case, the HER2 status converted from IHC2+ FISH not amplified to IHC3+. 3/8 patients had multifocal disease. All 6 patients with HR+/HER2- BC and HER2 gain had high (>90%) ER expression (Table 1). All but one patient with HER2 gain received adjuvant anti-HER2 therapy. After a median follow-up of 10 months, no recurrence events occurred in this group.12 of the remaining 184 patients experienced a recurrence [11 distant recurrences (8 and 3, in the TNBC and HR+/HER2- groups, respectively), and there was 1 local event (localized chest wall recurrence) in the HR+/HER2- group].

Conclusions: At a single center, we found that in patients with HER2- BC treated with NAC, HER2 gain in patients with RD was uncommon and occurred more frequently in those with HR+ tumors. Analysis of a larger cohort is ongoing to corroborate these results. It is remains to be determined if this phenomenon represents a true HER2 status conversion or tumor heterogeneity.

Table 1: Clinico-pathological characteristics of patients with HER2 gain on residual disease

Citation Format: Emanuela Ferraro, Sonya Chew Minmin, Anton Safonov, Andrea V. Barrio, Shanu Modi, Andrew D Seidman, Hanna Y Wen, Edi Brogi, Mark E. Robson, Chau T Dang. Gain of HER2 Amplification in Patients with HR+/HER2- and Triple Negative Early Breast Cancer Treated with Neoadjuvant Chemotherapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-02-14.

Histopathologic Grading Is of Prognostic Significance in Primary Angiosarcoma of Breast: Proposal of a Simplified 2-tier Grading System

Despite a wide spectrum of clinical presentations, including primary or secondary, most angiosarcomas are considered high grade. One exception is primary breast angiosarcoma, where historically, histologic grading has shown to predict outcome using the Rosen 3-tier system. However, more recent studies have challenged this concept suggesting that even in this specific clinical context angiosarcomas should be considered high grade. This study aimed to critically reevaluate the impact of histologic grade in a clinically uniform cohort managed at a single institution using a newly proposed grading system. Our study included 49 primary breast angiosarcomas diagnosed during 1994 to 2022 (median follow-up: 33 mo), classified as low grade (29%), intermediate grade (20%), and high grade (51%), based on mitotic count, extent of solid components, and necrosis. At last follow-up, 22% patients developed locoregional recurrences, 63% distant metastases, and 47% patients died of disease. As patients with low and intermediate-grade angiosarcomas had relatively similar outcomes, our cohort was further analyzed using a 2-tier system (low grade and high grade). Targeted-DNA next-generation sequencing (505 cancer gene panel) performed in 11 cases found KDR mutations in 78% and PIK3CA mutations in 44% of high-grade lesions. Histologic grade, by either 3-tier or 2-tier grading systems, had a strong impact on survival, with the 2-tier system being an independent predictor of disease-specific survival and overall survival. Based on 2-tier system, the 5-year overall survival was 38% for high-grade angiosarcoma and 74% for low-grade angiosarcoma. PIK3CA mutations alone or concurrent with KDR alterations were identified in angiosarcomas with worse prognosis.

Changes in the Diagnoses of Breast Core Needle Biopsies on Second Review at a Tertiary Care Center: Implications for Surgical Management

Core needle biopsy (CNB) of breast lesions is routine for diagnosis and treatment planning. Despite refinement of diagnostic criteria, the diagnosis of breast lesions on CNB can be challenging. At many centers, including ours, confirmation of diagnoses rendered in other laboratories is required before treatment planning. We identified CNBs first diagnosed elsewhere that were reviewed in our department over the course of 1 year because the patients sought care at our center and in which a change in diagnosis had been recorded. The outside and in-house CNB diagnoses were then classified based on Breast WHO Fifth Edition diagnostic categories. The impact of the change in diagnosis was estimated based on the subsequent surgical management. Findings in follow-up surgical excisions (EXCs) were used for validation. In 2018, 4950 outside cases with CNB were reviewed at our center. A total of 403 CNBs diagnoses were discrepant. Of these, 147 had a change in the WHO diagnostic category: 80 (54%) CNBs had a more severe diagnosis and 44 (30%) a less severe diagnosis. In 23 (16%) CNBs, the change of diagnostic category had no impact on management. Intraductal proliferations (n=54), microinvasive carcinoma (n=18), and papillary lesions (n=35) were the most disputed diagnoses. The in-house CNB diagnosis was confirmed in most cases with available excisions. Following CNB reclassification, 22/147 (15%) lesions were not excised. A change affecting the surgical management at our center occurred in 2.5% of all CNBs. Our results support routine review of outside breast CNB as a clinically significant practice before definitive treatment.

Distinct tumor architectures for metastatic colonization of the brain

Brain metastasis is a dismal cancer complication, hinging on the initial survival and outgrowth of disseminated cancer cells. To understand these crucial early stages of colonization, we investigated two prevalent sources of cerebral relapse, triple-negative (TNBC) and HER2+ breast cancer (HER2BC). We show that these tumor types colonize the brain aggressively, yet with distinct tumor architectures, stromal interfaces, and autocrine growth programs. TNBC forms perivascular sheaths with diffusive contact with astrocytes and microglia. In contrast, HER2BC forms compact spheroids prompted by autonomous extracellular matrix components and segregating stromal cells to their periphery. Single-cell transcriptomic dissection reveals canonical Alzheimer's disease-associated microglia (DAM) responses. Differential engagement of tumor-DAM signaling through the receptor AXL suggests specific pro-metastatic functions of the tumor architecture in both TNBC perivascular and HER2BC spheroidal colonies. The distinct spatial features of these two highly efficient modes of brain colonization have relevance for leveraging the stroma to treat brain metastasis.

Update on lobular lesions of the breast

The current histological classification of in-situ and invasive lobular carcinomas (ILCs) includes different morphological variants, some of which have been recently described. In this review, we will focus upon: (i) the diagnostic criteria of non-invasive lobular neoplasia and treatment implications across different countries; (ii) utility and limitations of immunohistochemistry; (iii) recently described variants of ILC; and (iv) the significance of lobular differentiation in invasive carcinoma for clinical management.

Cardiac complications in patients with COVID-19: a systematic review

Cardiac complications in patients with COVID-19 have been described in the literature with an important impact on outcome. The primary objective of our systematic review was to describe the kind of cardiac complications observed in COVID-19 patients and to identify potential predictors of cardiovascular events. The secondary aim was to analyze the effect of cardiac complications on outcome.

We performed this systematic review according to PRISMA guidelines using several databases for studies evaluating the type of cardiac complications and risk factors in COVID-19 patients. We also calculated the risk ratio (RR) and 95% CI. A random-effects model was applied to analyze the data. The heterogeneity of the retrieved trials was evaluated through the I² statistic. Our systematic review included 49 studies. Acute cardiac injury was evaluated in 20 articles. Heart failure and cardiogenic shock were reported in 10 articles. Myocardial infarction was evaluated in seven of the papers retrieved. Takotsubo, myocarditis, and pericardial effusion were reported in six, twelve, and five articles, respectively. Arrhythmic complications were evaluated in thirteen studies. Right ventricular dysfunction was evaluated in six articles. We included 7 studies investigating 2115 patients in the meta-analysis. The RR was 0.20 (95% CI: 0.17 to 0.24; P < 0.00001, I² = 0.75). Acute cardiac injury represented the prevalent cardiac complications observed in COVID-19 patients (from 20 to 45% of the patients). Patients with acute cardiac injury seemed to be significantly older, with comorbidities, more likely to develop complications, and with higher mortality rates. Acute cardiac injury was found to be an independent risk factor for severe forms of SARS-CoV-2 infection and an independent predictor of mortality. Due to the scarce evidence, it was not possible to draw any conclusion regarding Takotsubo, myocarditis, pleural effusion, and right ventricular dysfunction in COVID-19 patients. Noteworthy, possible arrhythmic alterations (incidence rate of arrhythmia from 3 to 60%) in COVID-19 patients have to be taken into account for the possible complications and the consequent hemodynamic instabilities. Hypertension seemed to represent the most common comorbidities in COVID-19 patients (from 30 to 59.8%). The prevalence of cardiovascular disease (CVD) was high in this group of patients (up to 57%), with coronary artery disease in around 10% of the cases. In the majority of the studies retrieved, patients with CVD had a higher prevalence of severe form, ICU admission, and higher mortality rates.

Reporting of Surgically Removed Lymph Nodes for Breast Tumors: Recommendations From the International Collaboration on Cancer Reporting

CONTEXT.—

The International Collaboration on Cancer Reporting (ICCR), supported by major pathology and cancer organizations, aims at the standardization of evidence-based pathology reporting of different types of cancers, with the inclusion of all parameters deemed to be relevant for best patient care and future data collection. Lymph node metastasis is one of the most important prognostic factors in breast cancer.

OBJECTIVE.—

To produce a histopathology reporting guide by a panel of recognized experts from the fields of pathology and surgery with elements deemed to be core (required) and noncore (recommended) to report when assessing regional lymph nodes of patients with breast cancer.

DATA SOURCES.—

Published literature, previous guidelines/recommendations, and current cancer staging principles were the basis of the data set drafted by the expert panel. This was discussed in a series of teleconferences and email communications. The draft data set was then made available for public consultation through the ICCR Web site. After this consultation and ICCR ratification, the data set was finalized.

CONCLUSIONS.—

The ICCR has published a data set for the reporting of surgically removed lymph nodes (including sentinel lymph node biopsy, axillary lymph node dissection, targeted axillary surgery, and lymph node sampling specimens) for breast tumors. This is part of a series of 4 ICCR breast cancer-related data sets. It includes 10 core elements along with 2 noncore elements. This should allow for synoptic reporting, which is more precise, uniform, and complete than nonsynoptic reporting, and leads to improved patient outcomes.

Expression of novel neuroendocrine markers in breast carcinomas: a study of INSM1, ASCL1, and POU2F3

INSM1, ASCL1, and POU2F3 are novel transcription factors involved in neuroendocrine (NE) differentiation of neoplasms in several organs, but data on their expression in breast carcinomas (BCs) are limited. We retrospectively evaluated the expression of these markers in a series of 97 BCs (58 with NE morphology and 39 with otherwise uncommon morphology) tested prospectively using immunohistochemistry (IHC). Nuclear staining in >50% of the cells was used as the positive cut-off. Thirty-two of the 97 BCs (33%) were INSM1-positive. INSM1-positivity correlated significantly with histologic type and presence of stromal mucin. INSM1 also correlated with synaptophysin and chromogranin, established markers of NE differentiation (P < .0001 and P = .0023, respectively). In BC with NE morphology, the expression of INSM1 supported NE differentiation, and INSM1 was more specific than synaptophysin and more sensitive and specific than chromogranin. INSM1 was the most expressed NE marker in 17 BCs. INSM1-positive BCs included 56% of solid papillary BCs, 88% of BCs with solid papillary features, and 75% of high-grade NE carcinomas. Of 35 BCs tested for POU2F3 and ASCL1, only 1 and 4 cases were positive, respectively. Our results show that INSM1 is a sensitive marker of NE differentiation in BC and should be included with synaptophysin and chromogranin in the IHC panel used to evaluate NE differentiation in BC with NE morphology. ASCL1 and POU2F3 are uncommon in BC and their routine assessment is not warranted.

Solid-basaloid variant of adenoid cystic carcinoma of the breast with near complete response to neoadjuvant chemotherapy

Breast adenoid cystic carcinoma (AdCC) is a rare subtype of triple negative breast cancer. Two morphologic variants are described, namely classic AdCC (C-AdCC) and solid basaloid (SB-AdCC). Recent studies have shown that the SB-AdCC variant has significantly worse prognosis than C-AdCC. Due to the rarity of SB-AdCC, no standard recommendations are available for its management. Data on the use and benefit of chemotherapy in patients with SB-AdCC are sparse and the response to neoadjuvant chemotherapy has not been reported. We present the clinical and pathologic findings of a patient with SB-AdCC treated with neoadjuvant chemotherapy who achieved a remarkable pathologic response.

Abstract 1928: Prediction of neoadjuvant treatment outcomes with multimodal data integration in breast cancer

Neoadjuvant chemotherapy (NAC) is the standard of care for selected patients with high-risk early-stage breast cancer with pathologic complete response (pCR) being the most prominent predictor of favorable outcomes. Here, we sought to study the predictive capacity of integrating orthogonal diagnostic measures on predicting pCR relative to standard clinicopathologic features.

We developed a computational model integrating radiology and pathology images, and tumor genomics to automatically predict pCR from multimodal data. We present an interim analysis on a cohort of 957 patients with at least one available pre-NAC data modality. The baseline AUC for pCR prediction by a trained and tested logistic regression model on 857 patients using standard clinicopathologic features including receptor subtype, demographic information, and stage was 0.77. MR images were input into a convolutional neural network (CNN) and a radiomics model.

The trained CNN and radiomics models using selected images of 576 patients with pre-NAC MR images achieved AUCs of 0.65 and 0.60 on 164 hold-out test cases, respectively.

We trained a multiple instance learning-based weakly supervised learning (MIL-WSL) model using 537,762 extracted tiles from whole slide images (WSI) of digital histopathology scans from 522 patients. The MIL-WSL model achieved AUC of 0.63 for pCR prediction on a hold-out test set of pre-NAC biopsies from 239 patients. A feature based classifier trained on 76 cases using tumor genomic features such as mutational burden, microsatellite instability, fraction genome altered, ploidy, purity, mutation and copy number alterations in selected genes achieved an AUC of 0.72 on 83 hold-out test cases.

We then combined unimodal radiology, histopathology, and genomic predictions in a deterministic manner. This multimodal combination on an independent 68-patient test set achieved an AUC of 0.84, indicating increased power to resolve pCR than any modality alone, and over clinicopathologic baseline.

Together, we present approaches to train models end-to-end using tensor fusion networks and attention-gating combined with MIL. Automated multimodal methods are here shown to improve prediction over established clinical parameters alone, motivating our ongoing efforts to refine and improve the model so as to achieve higher levels of efficiency. We anticipate these interim results will be further improved through refinement of input features and increasing the number of patients included in the final validation cohort.

Citation Format: Pegah Khosravi, Elizabeth J. Sutton, Justin Jee, Timothy Dalfonso, Christopher J. Fong, Doori Rose, Edaise M. Da Silva, Armaan Kohli, David Joon Ho, Mehnaj S. Ahmed, Danny Martinez, Anika Begum, Elizabeth Zakszewski, Andrew Aukerman, Yanis Tazi, Katja Pinker-Domenig, Sarah Eskreis-Winkler, Atif J. Khan, Edi Brogi, Elizabeth Morris, Sarat Chandarlapaty, George Plitas, Simon Powell, Monica Morrow, Larry Norton, Jianjiong Gao, Mark Robson, Hong Zhang, Sohrab Shah, Pedram Razavi, MSK-MIND Consortium. Prediction of neoadjuvant treatment outcomes with multimodal data integration in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1928.

Quality Issues in Diagnostic Immunohistochemistry in Breast Pathology

Immunohistochemistry techniques have been incorporated into surgical pathology for nearly a half-century and have since become intimately intertwined with its practice. In the realm of breast pathology, immunohistochemistry serves several purposes, including providing crucial prognostic and predictive data. Among its other applications, assessment of stromal invasion and establishment of mammary origin are crucial from a diagnostic standpoint. In these regards, sole reliance on immunohistochemistry may lead to misdiagnosis. In this review, we highlight pitfalls of immunohistochemistry commonly encountered in the practice of breast pathology and emphasize the importance of careful histopathological evaluation.

Incidence of brain metastases in patients with early HER2-positive breast cancer receiving neoadjuvant chemotherapy with trastuzumab and pertuzumab

The addition of pertuzumab (P) to trastuzumab (H) and neoadjuvant chemotherapy (NAC) has decreased the risk of distant recurrence in early stage HER2-positive breast cancer. The incidence of brain metastases (BM) in patients who achieved pathological complete response (pCR) versus those who do not is unknown. In this study, we sought the incidence of BM in patients receiving HP-containing NAC as well as survival outcome. We reviewed the medical records of 526 early stage HER2-positive patients treated with an HP-based regimen at Memorial Sloan Kettering Cancer Center (MSKCC), between September 1, 2013 to November 1, 2019. The primary endpoint was to estimate the cumulative incidence of BM in pCR versus non-pCR patients; secondary endpoints included disease free-survival (DFS) and overall survival (OS). After a median follow-up of 3.2 years, 7 out of 286 patients with pCR had a BM while 5 out of 240 non-pCR patients had a BM. The 3-year DFS was significantly higher in the pCR group compared to non-pCR group (95% vs 91 %, p = 0.03) and the same trend was observed for overall survival. In our cohort, despite the better survival outcomes of patients who achieved pCR, we did not observe appreciable differences in the incidence of BM by pCR/non-pCR status. This finding suggests that the BM incidence could not be associated with pCR. Future trials with new small molecules able to cross the blood brain barrier should use more specific biomarkers rather than pCR for patients' selection.

Androgen receptor splice variant-7 in breast cancer: clinical and pathologic correlations

Androgen receptor (AR) inhibitor therapy is a developing treatment for AR-positive breast cancer (BC) with ongoing clinical trials. AR splice variant-7 (AR-V7) is a truncated variant of AR that leads to AR inhibitor therapy resistance in prostate cancer; recent studies have identified AR-V7 in BC and theorized that AR-V7 can have a similar impact. This study assessed the prevalence and clinicopathologic features associated with AR-V7 in a large BC cohort. BC samples were evaluated by MSK-Fusion targeted RNAseq for AR-V7 detection and MSK-IMPACT targeted DNAseq, including triple-negative tumors with no driver alteration and estrogen receptor-positive/ESR1 wildtype tumors progressing on therapy. Among 196 primary and metastatic/recurrent cases (196 RNAseq, 194DNAseq), 9.7% (19/196) were AR-V7 positive and 90.3% (177/196) AR-V7 negative. All AR-V7 positive BC were AR-positive by immunohistochemistry (19/19). The prevalence of AR-V7 by receptor subtype (N = 189) was: 18% (12/67) in ER-/PgR-/HER2-negative BC, 3.7% (4/109) in ER-positive/HER2-negative BC, and 15.4% (2/13) in HER2-positive BC; AR-V7 was detected in one ER-positive/HER2-unknown BC. Apocrine morphology was observed in 42.1% (8/19) of AR-V7 positive BC and 3.4% (6/177) AR-V7 negative BC (P < 0.00001). Notably, AR-V7 was detected in 2 primary BC and 7 metastatic/recurrent BC patients with no prior endocrine therapy. We conclude that positive AR IHC and apocrine morphology are pathologic features that may indicate testing for AR-V7 is warranted in both primary and metastatic BC in the appropriate clinical context. The study findings further encourage the assessment of AR-V7 as a predictive biomarker for AR antagonist benefit in ongoing clinical BC trials.

Abstract P2-13-06: Clinical implication of HER2 status change after neoadjuvant chemotherapy with Trastuzumab and Pertuzumab (HP) in patients with HER2-positive breast cancer

Background: Patients with early HER2-positive breast cancer (BC) and residual disease after HER2-targeted neoadjuvant chemotherapy (NAC) are at high risk of recurrence. It is estimated that 10-30% of HER2-positive breast cancers change HER2 status after trastuzumab alone, but the effects of adding pertuzumab on this phenomenon and clinical outcomes remain unclear. We previously reported a high rate (~50%) of HER2 status change after HP in a small subset of patients. Herein, we present an updated analysis incorporating pathological review of additional cases.Methods: We identified patients with HER2-positive BC who received NAC with pertuzumab and trastuzumab (NAC-HP) followed by surgery at our institution between September 1, 2013 to November 1, 2019. Patients with HER2 status performed either at MSKCC or outside institutions were included. Change in HER2 status on residual disease from baseline was evaluated. We defined HER2 positivity as immunohistochemistry (IHC) IHC3+ or IHC0-2+ FISH amplified (ratio ≥ 2 or ratio &lt; 2 and HER2 copy number ≥ 6 signals/cell). HER2-low was defined as IHC 1+ or 2+, FISH non-amplified. Disease free survival (DFS) and overall survival (OS) were analyzed using the Kaplan-Meier method. Differences between patients with concordant and discordance HER2 status were assessed using the log-rank test.Results: Of 525 patients receiving NAC with HP, 229 (44%) patients had residual disease post NAC-HP. Among these 229 patients, 141 had both pre and post NAC-HP HER2 status available and were included in this analysis. HER2 status on biopsy specimens was determined at MSKCC in 35/141 (25%) and at external institution in 106/141 (75%). The majority of patients (84%) received dose-dense AC-THP; the remainder received TCHP or other HP-based regimens. Most (96%) of patients continued HP after surgery, and 2 patients received T-DM1. Of the 141 patients, 84/141(60%) were found to be HER2 concordant, while 57 (40%) were found to be HER2 discordant. In 13/57 (23%) patients, HER2 expression was lost (IHC 0), while in 44/57 (77%) patients, HER2-low profile was detected (IHC 1+ in 31, and IHC 2+, FISH non-amplified in 13). Further details are reported in the table. Patients with HER2 discordance after NAC-HP had similar survival outcome compared with patients who remained HER2 concordant (5-years DFS: 92.3% versus 88.7%, p=0.49 and 5-yr OS 93.6% versus 88.4%, p=0.70).Conclusions: In a single center cohort, discordant HER2 status after NAC-HP appeared frequently without statistically significant impact on survival outcome, although this finding may be due to the small size and hence low statistical power. Of these, HER2-low profile is the most frequent post treatment HER2 status change. This raises the possibility that patients with change in HER2 status may have heterogenous expression of HER2 at baseline, and HER2-loss or low sub-clones survive as residual disease due to the selection pressure of HP. Alternatively, anti-HER2 therapy may suppress HER2 expression in surviving cells. These findings could inform studies of tailored approaches in the post-neoadjuvant setting based on the biological profile of residual disease.

Pre NAC-HP HER2 statusNPost NAC-HP HER2 statusNDiscordantN=57IHC 3+: 19IHC0: 4IHC1+: 9IHC2+ FISH not ampl: 6IHC 0-2+ FISH ampl: 38IHC0: 9IHC1+: 22IHC2+ FISH not ampl: 7Concordant N= 84IHC 3+: 59IHC 3+: 47IHC 0- 2+ FISH ampl: 12IHC 0-2+ FISH ampl: 25IHC 3+: 4IHC 0- 2+ FISH ampl: 21

Citation Format: Emanuela Ferraro, Anton Safonov, Hanna Y Wen, Edi Brogi, Mithat Gonan, Andrea V. Barrio, Pedram Razavi, Sarat Chandarlapaty, Shanu Modi, Andrew D. Seidman, Larry Norton, Mark E. Robson, Chau T. Dang. Clinical implication of HER2 status change after neoadjuvant chemotherapy with Trastuzumab and Pertuzumab (HP) in patients with HER2-positive breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-06.

Abstract PD11-01: An artificial intelligence-based predictor of CDH1 biallelic mutations and invasive lobular carcinoma

Introduction: Invasive lobular carcinoma (ILC) is the most frequent special histologic subtype of breast cancer (BC). ILC is identifiable by pathologic assessment given its distinctive discohesive growth pattern, largely caused by CDH1 inactivation. Compared to common forms of BC, ILCs display lower responses to chemotherapy and selective estrogen receptor modulators. The low interobserver agreement for the diagnosis of ILC, however, renders the inclusion of histologic subtyping in therapeutic decision-making challenging. Artificial intelligence (AI)-based algorithms hold promise for improving pathologic diagnosis; their performance, however, depends on the ground truth labeling used. Here, we seek to develop an AI-based methodology for detection of ILC using ‘CDH1 biallelic mutations’ (i.e., mutation + loss-of-heterozygosity of the wild-type allele or two pathogenic somatic mutations) as ground truth, reasoning that in BC, &gt;95% of CDH1 bi-allelic inactivation is found in ILCs.Materials and methods: We developed a convolutional neural network system to detect CDH1 biallelic genetic inactivation (AI-CDH1) using whole slide images (WSI) of 1,100 primary BCs with available targeted sequencing data. The model was trained using a 10-fold cross-validation method to detect biallelic mutations. The mean number of positive and negative samples in the training set was 85.2 (SD=2.57) and 562.8 (SD=10.51) per fold, respectively. The evaluation set consisted of a mean of 14.2 (SD=2.04) positive and 93.8 (SD=9.13) negative samples. We evaluated the performance of the AI-CDH1 classifier to predict the lobular phenotype and CDH1 status using original and revised labels, following a histopathologic re-review of the histologic type and CDH1 status curation. The latter was conducted by incorporating information on biallelic CDH1 inactivation beyond CDH1 mutations (homozygous deletions, deleterious structural rearrangements, and loss-of-heterozygosity and gene promoter methylation).Results: The AI-CDH1 classifier predicted biallelic CDH1 mutations with an area under the curve (AUC)=0.944 (95 CI: 0.925-0.963), sensitivity=91.6% and specificity=85.9%, PPV=49.8%, NPV=98.5% and accuracy=86.7%, and the original ‘lobular phenotype’ with an AUC=0.941 (95 CI: 0.922-0.960), sensitivity=89%, specificity=86.7%, PPV=55.6%, NPV=97.7% and accuracy=87.1%. Review of the CDH1 gene status revealed that 7/957 BCs lacking CDH1 biallelic mutations harbored biallelic CDH1 inactivation by promoter methylation, homozygous deletions or structural rearrangements. The AI-CDH1 classifier detected all seven reclassified BCs and predicted the revised CDH1 biallelic inactivation with an AUC=0.948 (95 CI: 0.930-0.966), sensitivity=92%, specificity=86.5%, PPV=52.3%, NPV=98.5% and accuracy=87.2%. Upon histologic re-review, which resulted in reclassification of 36/927 non-lobular BCs as ‘lobular’ and 5/173 ‘lobular’ BCs as ‘non-lobular’, the AI-CDH1 classifier detected the ‘lobular phenotype’ with an AUC=0.953 (95 CI: 0.935-0.971), sensitivity=90.7%, specificity=89.7%, PPV=66.8%, NPV=97.7% and accuracy=89.9%. Using the revised histologic re-classification and CDH1 biallelic inactivation status labels, the AI-CDH1 classifier predicted the lobular phenotype irrespective of CDH1 status (P&gt;0.05).Conclusions: By training a machine learning system to detect ‘CDH1 biallelic mutations’, as ground truth rather than histologic diagnosis of lobular carcinoma, which might be confounded by human subjectivity, we developed an AI-based system that can detect ILCs accurately, providing a new paradigm for the development of AI-based cancer classification systems.

Citation Format: Jorge S Reis-Filho, Fresia Pareja, Fatemeh Derakhshan, David N Brown, Jillian Sue, Pier Selenica, Yi Kan Wang, Arnaud Da Cruz Paula, Monami Banerjee, Zahra Ebrahimzadeh, Manuel Isava, Matthew Lee, Ran Godrich, Adam Casson, Ruben Padron, George Shaikovski, Alexander van Eck, Antonio Marra, Higinio Dopeso, Hannah Y Wen, Edi Brogi, Matthew G Hanna, Chris Kanan, Jeremy D Kunz, Felipe C Geyer, Carla Leibowitz, David Klimstra, Leo Grady, Thomas J Fuchs. An artificial intelligence-based predictor of CDH1 biallelic mutations and invasive lobular carcinoma [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD11-01.

Abstract PD14-03: Genetic and epigenetic basis of invasive lobular carcinomas lacking CDH1-alterations

Introduction: Invasive lobular carcinoma (ILC) is the most prevalent histologic special type of breast cancer, representing ~15% of invasive breast cancers. ILCs are mostly hormone receptor-positive and diagnosed histologically based on their distinctive discohesive growth pattern, dispersed single cells or line of cells invading the stroma. ILCs commonly show biallelic inactivation of a CDH1 (~65%), a tumor suppressor gene that is mapped to 16q22.1 and encodes for E-cadherin, a critical component of the epithelial adhesion complex. Massively parallel sequencing and pathologic studies have shown that a subset of ILCs (up to 15%) may lack CDH1 loss-of-function (LOF) mutations/deletions and retain E-cadherin expression, despite their distinctive lobular phenotype. The genetic and epigenetic underpinning of ILCs lacking CDH1 alterations has yet to be defined. Here we sought to define the mechanistic basis of the lobular phenotype in ILCs lacking CDH1 LOF genetic alterations or CDH1 gene promoter methylation and to determine the repertoire of epigenetic and genetic alterations of CDH1-wildtype ILCs. Materials and methods: Reanalysis of the CDH1 gene status in 364 primary ILCs, previously subjected to clinical massively parallel sequencing, was performed to identify all primary ILCs lacking bi-allelic CDH1 alterations. The hematoxylin and eosin stained slides of all identified ILCs lacking bi-allelic CDH1 alterations were reviewed by two pathologists and primary pure ILCs lacking bi-allelic CDH1 alterations were curated. We evaluated the presence of genetic alterations in genes playing essential roles in epithelial adhesion included in the clinical sequencing panel of up to 505 genes. The presence of CDH1 promoter methylation in 18 ILCs lacking bi-allelic CDH1 alterations with available formalin-fixed, paraffin-embedded (FFPE) material was assessed using methylation-specific PCR (MSP) and bisulfite sequencing. Results: We identified 23/364 (6.3%) primary ILCs lacking bi-allelic CDH1 alterations, of which 65.3% and 34.7% were classic and pleomorphic lobular variants, respectively. In 18 cases with available FFPE material, our analyses revealed that 67% (12/18) of ILCs lacking bi-allelic CDH1 alterations displayed biallelic CDH1 inactivation via promoter methylation and 16q loss. Furthermore, we observed that 1/23 ILC lacking bi-allelic CDH1 alterations had bi-allelic inactivation of AXIN2. We then extended our query to all invasive breast carcinomas subjected to clinical sequencing, including the ones initially categorized as invasive breast carcinoma “type unknown”, and observed that the three additional cases with pathogenic LOF AXIN2 alterations were ILCs lacking bi-allelic CDH1 alterations. Conclusions: The lobular phenotype in ILCs can be due to CDH1 promoter methylation or genetic alterations affecting other genes related to epithelial cell adhesion, such as AXIN2 LOF mutations. Whole-genome sequencing analyses of ILCs whose molecular basis has not been identified by targeted sequencing are warranted.

Citation Format: Fatemeh Derakhshan, Higinio Dopeso, Arnaud Da Cruz Paula, Pier Selenica, Antonio Marra, Edaise M da Silva, Andrea Gazzo, Shirin Issa Bhaloo, Dara S Ross, Anne Grabenstetter, Sarat Chandarlapaty, Pedram Razavi, Hannah Y. Wen, Hong Zhang, Edi Brogi, Britta Weigelt, Fresia Pareja, Jorge S. Reis-Filho. Genetic and epigenetic basis of invasive lobular carcinomas lacking CDH1-alterations [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD14-03.

Expression Analysis of GD2 by Immunohistochemistry in Invasive Breast Carcinoma: Clinical and Pathologic Correlation

The glycosphingolipid disialoganglioside GD2 is a cell surface-associated antigen expressed on tumors of neuroectodermal origin that serves as a target of immunotherapy in select cancer types. Information about the expression of GD2 in breast cancer is limited. In the present study, we investigate the utility of GD2 as a potential biomarker for targeted treatment. The study cohort consists of 386 breast carcinomas of several histologic types. GD2 expression was assessed in both whole tumor sections and tissue microarrays with anti-GD2 3F8 monoclonal antibody immunohistochemistry and correlated with clinicopathologic features and survival outcomes. A total of 134 (35%) breast carcinomas were positive for GD2, with a median H-score of 100. 3F8 staining displayed granular and predominantly cytoplasmic or perinuclear patterns, which was confined to the neoplastic tissue in nearly all cases. GD2 positivity was significantly associated with tumor histologic type (P=0.0015), low grade (P<0.0001), estrogen receptor positivity (P<0.0001), low stage (P=0.0014), and multifocality (P=0.022). Event-free survival and overall survival of patients with GD2-positive and GD2-negative tumors were not significantly different. Our results support further assessment of GD2 using the 3F8 antibody as a predictive and prognostic biomarker in breast cancer.

Digital validation of breast biomarkers (ER, PR, AR, and HER2) in cytology specimens using three different scanners

Progression in digital pathology has yielded new opportunities for a remote work environment. We evaluated the utility of digital review of breast cancer immunohistochemical prognostic markers (IHC) using whole slide images (WSI) from formalin fixed paraffin embedded (FFPE) cytology cell block specimens (CB) using three different scanners.CB from 20 patients with breast cancer diagnosis and available IHC were included. Glass slides including 20 Hematoxylin and eosin (H&E), 20 Estrogen Receptor (ER), 20 Progesterone Receptor (PR), 16 Androgen Receptor (AR), and 20 Human Epidermal Growth Factor Receptor 2 (HER2) were scanned on 3 different scanners. Four breast pathologists reviewed the WSI and recorded their semi-quantitative scoring for each marker. Kappa concordance was defined as complete agreement between glass/digital pairs. Discordances between microscopic and digital reads were classified as a major when a clinically relevant change was seen. Minor discordances were defined as differences in scoring percentages/staining pattern that would not have resulted in a clinical implication. Scanner precision was tabulated according to the success rate of each scan on all three scanners.In total, we had 228 paired glass/digital IHC reads on all 3 scanners. There was strong concordance kappa ≥0.85 for all pathologists when comparing paired microscopic/digital reads. Strong concordance (kappa ≥0.86) was also seen when comparing reads between scanners.Twenty-three percent of the WSI required rescanning due to barcode detection failures, 14% due to tissue detection failures, and 2% due to focus issues. Scanner 1 had the best average precision of 92%. HER2 IHC had the lowest intra-scanner precision (64%) among all stains.This study is the first to address the utility of WSI in breast cancer IHC in CB and to validate its reporting using 3 different scanners. Digital images are reliable for breast IHC assessment in CB and offer similar reproducibility to microscope reads.

Neuroendocrine tumours of the breast: a genomic comparison with mucinous breast cancers and neuroendocrine tumours of other anatomic sites

AIMS

Breast neuroendocrine tumours (NETs) constitute a rare histologic subtype of oestrogen receptor (ER)-positive breast cancer, and their definition according to the WHO classification was revised in 2019. Breast NETs display histologic and transcriptomic similarities with mucinous breast carcinomas (MuBCs). Here, we sought to compare the repertoire of genetic alterations in breast NETs with MuBCs and NETs from other anatomic origins.

METHODS

On histologic review applying the new WHO criteria, 18 breast tumours with neuroendocrine differentiation were reclassified as breast NETs (n=10) or other breast cancers with neuroendocrine differentiation (n=8). We reanalysed targeted sequencing or whole-exome sequencing data of breast NETs (n=10), MuBCs type A (n=12) and type B (n=11).

RESULTS

Breast NETs and MuBCs were found to be genetically similar, harbouring a lower frequency of PIK3CA mutations, 1q gains and 16q losses than ER-positive/HER2-negative breast cancers. 3/10 breast NETs harboured the hallmark features of ER-positive disease (ie, PIK3CA mutations and concurrent 1q gains/16q losses). Breast NETs showed an enrichment of oncogenic/likely oncogenic mutations affecting transcription factors compared with common forms of ER-positive breast cancer and with pancreatic and pulmonary NETs.

CONCLUSIONS

Breast NETs are heterogeneous and are characterised by an enrichment of mutations in transcription factors and likely constitute a spectrum of entities histologically and genomically related to MuBCs. While most breast NETs are distinct from ER-positive/HER2-negative IDC-NSTs, a subset of breast NETs appears to be genetically similar to common forms of ER-positive breast cancer, suggesting that some breast cancers may acquire neuroendocrine differentiation later in tumour evolution.

Morphological and genomic characteristics of breast cancers occurring in individuals with Lynch Syndrome

PURPOSE

Lynch syndrome (LS) is defined by germline pathogenic mutations involving DNA Mismatch Repair (MMR) genes and linked with the development of MMR-deficient (MMRd) colon and endometrial cancers. Whether breast cancers (BC) developing in context of LS are causally related to MMR deficiency (MMRd), remains controversial. Thus, we explored the morphological and genomic characteristics of BCs occurring in LS individuals.

EXPERIMENTAL DESIGN

A retrospective analysis of 20,110 cancer patients who underwent multigene panel genetic testing was performed to identify individuals with a likely pathogenic/pathogenic germline variant in MLH1, MSH2, MSH6 or PMS2 who developed BCs. The histological characteristics and immunohistochemical (IHC) assessment of BCs for MMR proteins and programmed death-ligand 1 (PD-L1) expression were assessed on cases with available materials. DNA samples from paired tumors and blood were sequenced with MSK-IMPACT ({greater than or equal to}468 key cancer genes). MSI status was assessed utilizing MSISensor. Mutational signatures were defined using SigMA.

RESULTS

272 LS individuals were identified, 13 (5%) of whom had primary BCs. The majority of BCs (92%) were hormone receptor positive tumors. Five (42%) of 12 BCs displayed loss of MMR proteins by IHC. Four (36%) of 11 BCs subjected to tumor-normal sequencing showed dominant microsatellite instability mutational signatures, high tumor mutational burden and indeterminate (27%) or high MSISensor scores (9%). One patient with metastatic MMRd BC received anti-PD1 therapy and achieved a robust and durable response.

CONCLUSIONS

A subset of BCs developing in LS individuals are etiologically linked to MMRd and may benefit from anti-PD1/PD-L1 immunotherapy.

PD-L1 Expression in Metaplastic Breast Carcinoma Using the PD-L1 SP142 Assay and Concordance Among PD-L1 Immunohistochemical Assays

Immunotherapy for the treatment of programmed death-ligand 1 (PD-L1) positive locally advanced or metastatic triple negative breast cancer may benefit patients with metaplastic breast cancer (MpBC). Previous study of PD-L1 in MpBC scored tumor cells (TCs), different from Food and Drug Administration-approved scoring methods. We sought to define PD-L1 expression in MpBCs and to evaluate concordance of 3 PD-L1 assays. Primary, treatment naive MpBC treated at our Center from 1998 to 2019 were identified. PD-L1 expression was assessed using SP142, E1L3n, and 73-10. We evaluated PD-L1 expression on tumor infiltrating immune cells (IC) and also in TCs. For each assay, we scored PD-L1 expression using ≥1% IC expression according to the IMpassion130 trial criteria and using combined positive score (CPS) ≥10 according to the KEYNOTE-355 trial cutoff. A total of 42 MpBCs were identified. Most MpBC had PD-L1 positivity in ≥1% IC with all 3 assays (95%, 95%, 86%) in contrast to a maximum 71% with a CPS ≥10. PD-L1 IC expression was comparable between the SP142 and 73-10 assays and was lowest with E1L3n. PD-L1 TC expression was lowest using SP142. The overall concordance for IC scoring was 88% while 62% had concordant CPS. For each assay, the results of the 2 scoring algorithms were not interchangeable. The SP142 assay showed distinct expression patterns between IC (granular, dot-like) and TC (membranous) while 73-10 and E1L3n showed membranous and/or cytoplasmic expression in both IC and TC. Most MpBC in our cohort were positive for PD-L1 indicating eligibility for anti-PD-L1/programmed death-1 immunotherapy.

Triple-Positive Breast Carcinoma: Histopathologic Features and Response to Neoadjuvant Chemotherapy

CONTEXT.—

It is unclear whether HER2+ tumors expressing both estrogen receptor (ER) and progesterone receptor (PR), that is, triple-positive breast carcinomas (TPBCs), show unique morphologic and clinical features and response to neoadjuvant chemotherapy (NAC).

OBJECTIVE.—

To study the morphologic and immunohistochemical features of TPBCs from patients who underwent NAC.

DESIGN.—

We retrospectively reviewed core biopsy and post-NAC slides of 85 TPBCs. H-scores were calculated for ER and PR. HER2 slides and fluorescence in situ hybridization (FISH) reports were reviewed. Residual cancer burden was calculated for post-NAC specimens.

RESULTS.—

Eighty-one of the 85 tumors (95.3%) showed ductal histology, 3 (3.5%) were invasive lobular carcinomas, and 1 (1.2%) showed mixed ductal and lobular features. A subset showed mucinous (n = 7, 8.2%), apocrine (n = 5, 5.9%), and/or micropapillary (n = 4, 4.7%) differentiation. Fifty-four TPBCs (63.5%) showed high ER expression (H-score >200), including 27 (31.8%) with high expression of ER and PR. Fifty-two tumors (61.1%) showed HER2 3+ staining. Mean HER2/CEP17 ratio by FISH was 3.6 (range, 2-12.2) and mean HER2 signals per cell was 8 (range, 3.7-30.4). Pathologic complete response (pCR) rate was 35.3% (30 of 85). HER2 3+ staining was the only significant predictor of pCR on multivariate analysis (odds ratio = 9.215; 95% CI, 2.401-35.371; P < .001). The ER/PR expression did not correlate with response to therapy.

CONCLUSIONS.—

TPBCs are heterogeneous with some showing mucinous, lobular, or micropapillary differentiation. The pCR rate of TPBCs is similar to that reported for ER+/PR-/HER2+ tumors. HER2 overexpression by IHC was associated with significantly better response to therapy and may help select patients for treatment in the neoadjuvant setting.

Morphologic subtypes of lobular carcinoma in situ diagnosed on core needle biopsy: clinicopathologic features and findings at follow-up excision

Lobular carcinoma in situ (LCIS) is currently classified as classic (CLCIS), florid (FLCIS), and pleomorphic (PLCIS). Given the rarity of FLCIS and PLCIS, information on their clinico-pathologic features and biologic potential remains limited. We evaluated the upgrade rates at excision of FLCIS and PLCIS diagnosed on inhouse core needle biopsy (CNB) and their clinical presentation and follow-up. Over a period of 11 and a half years, there were a total of 36 inhouse CNBs with pure PLCIS (n = 8), FLCIS (n = 24), or LCIS with pleomorphic features (LCIS-PF) (n = 4). The upgrade rates to invasive carcinoma or ductal carcinoma in situ (DCIS) were 25% for PLCIS (2/8), 17% for FLCIS (4/24), and 0% for LCIS-PF (0/4). The overall upgrade rate of PLCIS and FLCIS combined was 19% (6/32). All but one case (not upgraded at excision) were radiologic-pathologic concordant. Apocrine features, previously reported only in PLCIS, were also noted in FLCIS. HER2 overexpression was seen in 13% of cases. This study highlights the more aggressive biologic features of PLCIS and FLCIS compared to CLCIS and supports surgical management for these lesions.

Spindle cell lesions of the breast: a diagnostic approach

Spindle cell lesions of the breast comprise a heterogeneous group of lesions, ranging from reactive and benign processes to aggressive malignant tumours. Despite their rarity, they attract the attention of breast pathologists due to their overlapping morphological features and diagnostic challenges, particularly on core needle biopsy (CNB) specimens. Pathologists should recognise the wide range of differential diagnoses and be familiar with the diverse morphological appearances of these lesions to make an accurate diagnosis and to suggest proper management of the patients. Clinical history, immunohistochemistry, and molecular assays are helpful in making a correct diagnosis in morphologically challenging cases. In this review, we present our approach for the diagnosis of breast spindle cell lesions, highlighting the main features of each entity and the potential pitfalls, particularly on CNB. Breast spindle cell lesions are generally classified into two main categories: bland-appearing and malignant-appearing lesions. Each category includes a distinct list of differential diagnoses and a panel of immunohistochemical markers. In bland-appearing lesions, it is important to distinguish fibromatosis-like spindle cell metaplastic breast carcinoma from other benign entities and to distinguish fibromatosis from scar tissue. The malignant-appearing category includes spindle cell metaplastic carcinoma, stroma rich malignant phyllodes tumour, other primary and metastatic malignant spindle cell tumours of the breast, including angiosarcoma and melanoma, and benign mimics such as florid granulation tissue and nodular fasciitis.

Poor response to neoadjuvant chemotherapy in metaplastic breast carcinoma

Metaplastic breast carcinoma (MpBC) is a rare special histologic subtype of breast carcinoma characterized by the presence of squamous and/or mesenchymal differentiation. Most MpBCs are of triple-negative phenotype and neoadjuvant chemotherapy (NAC) is frequently utilized in patients with MpBC. The aim of this study was to evaluate response to NAC in a retrospective cohort of MpBCs. We identified 44 patients with MpBC treated with NAC at our center between 2002 and 2018. Median age was 48 years, 86% were clinical stage II-III, and 36% were clinically node-positive. Most (80%) MpBCs were triple-negative or low (1-10%) hormonal receptor positive and HER2 negative on pre-NAC biopsy. While on NAC, 49% showed no clinical response or clinico-radiological progression. Matrix-producing subtype was associated with clinico-radiological response (p = 0.0036). Post NAC, two patients initially ineligible for breast-conserving surgery (BCS) were downstaged to be eligible for BCS, whereas three patients potentially eligible for BCS before treatment became ineligible due to disease progression. Only one (2%) patient had a pathologic complete response (pCR). Among the 16 patients presenting with biopsy-proven clinical node-positive disease, 3 (19%) had nodal pCR. Axillary lymph node dissection was avoided in 3 (19%) patients who had successful axillary downstaging. Residual cancer burden (RCB) was assessed in 22 patients and was significantly associated with disease-free survival and overall survival. We observed a poor response or even disease progression on NAC among patients with MpBC, suggesting that NAC should be reserved for patients with inoperable MpBC.

Morphologic and immunohistochemical features of carcinoma involving microglandular adenosis of the breast following neoadjuvant chemotherapy

Microglandular adenosis (MGA)-related lesions, including atypical MGA (AMGA) and carcinoma involving MGA (C-MGA), are characterized by epithelial atypia, negative hormone receptors, and HER2 status, and can mimic invasive triple negative breast cancer (TNBC) in core needle biopsies (CNB) resulting in selection for treatment with neoadjuvant chemotherapy (NAC). We identified 12 cases of AMGA and/or C-MGA in post-NAC excision specimens (EXC) and analyzed their morphologic and immunohistochemical (IHC) features. All CNBs were initially diagnosed as containing TNBC. Upon re-review, TNBC was confirmed in nine cases. In three CNBs AMGA and/or C-MGA had been interpreted as TNBC. AMGA was initially recognized in only one case but AMGA and/or C-MGA were present in an additional nine CNBs. At EXC, no residual TNBC was present in 5 of 9 EXCs and all 12 cases showed residual AMGA and/or C-MGA. Similar to conventional MGA, AMGA, and C-MGA were positive for S-100, laminin and collagen IV and negative for calponin and p63. Following NAC, these lesions retained their typical staining pattern despite acquiring treatment-related morphologic alterations, most notably of which were areas of single cell growth pattern seen in eight EXCs. This study is the first to report the effects of NAC on AMGA and C-MGA. Our data showed no response of the AMGA and/or C-MGA following NAC in contrast to the high response rate of conventional TNBC. In particular, the infiltrative single cell pattern of post-NAC MGA-related lesions closely mimicked residual TNBC. The persistence of AMGA and C-MGA following NAC supports the notion that these lesions are distinct from conventional TNBC. Our findings also highlight the challenges in recognizing AMGA and C-MGA in CNBs which may lead to unwarranted treatment with NAC in the absence of conventional TNBC.

The impact of MYC amplification on clinicopathologic features and prognosis of radiation-associated angiosarcomas of the breast

AIMS

Radiation-associated angiosarcomas (RT-AS) of the breast are rare tumours with poor prognosis. MYC amplification is considered the hallmark of RT-AS and is sometimes used as a diagnostic tool to distinguish from other radiation-associated vascular lesions. However, a small subset of RT-AS lacks MYC amplification, which may be associated with better outcome. Loss of H3K27me3 expression by immunohistochemistry (IHC) has been recently postulated as an additional diagnostic marker for RT-AS. This study aimed to evaluate the impact of MYC amplification as detected by fluorescence in situ hybridization and/or next-generation sequencing on clinicopathologic features and outcome in a large cohort of RT-AS, compare outcome with radiation-associated sarcomas of the breast (RT-S) other than angiosarcoma, and evaluate expression of H3K27me3 IHC in these groups.

METHODS AND RESULTS

Eighty-one RT-AS were identified, including 73 MYC amplified and 8 (10%) non-amplified. MYC amplified RT-AS were diagnosed in older patients (median age 69 vs 61 years). The 5-year disease specific survival and overall survival were 56% and 47%, respectively. Older age, larger tumour size, positive margin and MYC amplification were associated with worse prognosis. None of the RT-AS showed complete loss of H3K27me3 IHC expression. All 18 RT-S were MYC non-amplified, and complete loss of H3K27me3 expression was seen in 2. We found no difference in prognosis between RT-AS and RT-S.

CONCLUSIONS

RT-AS is associated with a poor prognosis. Older age at diagnosis, larger tumour size, positive margin at excision and MYC amplification are associated with worse prognosis.

Change in HER2 status after neoadjuvant chemotherapy (NAC) with trastuzumab and pertuzumab (HP) in patients with HER2-positive early-stage breast cancer

e12614

Background: Combination of HP with NAC in the neoadjuvant setting leads to an high rate of pathological complete response (pCR) in patients with stage II-III HER2+ breast cancer (BC). The rate of change in HER2-status after NAC reported in literature is between 10-30%, although NAC comprises a various regimens, and the clinical significance of this phenomenon is unclear. Methods: We extracted data on patients with HER2+ BC treated with NAC and HP between September 1, 2013 to November 1, 2019. Only patients with internally verified HER2 status at our center were enrolled. The rate of pCR (ypT0/is ypN0) and the change in HER2 status on residual disease from baseline were evaluated. We used standard definition of HER2 status based on ASCO/CAP guidelines 2018. HER2-low was defined as immunohistochemistry (IHC) 1+ or 2+, FISH non-amplified. Results: Overall, 130 pts were identified. All patients received dose-dense AC-THP, except for 13 patients who received TCHP or other HP-based regimens. The pCR was achieved in 77/130 (59%) of patients and 53/130 (41%) had residual disease. Among 53 patients with residual disease, HER2 status was analyzed in 25 patients and was pending on the remaining patients. In the 25 analyzed patients, 13 had HER2-loss in residual disease. In 4/13 patients, HER2 expression was lost (IHC 0); in 9/13 patients, HER2-low profile was found (IHC 1+ in 6 patients, and IHC 2+, FISH non-amplified in 3). Details on HER2 status change are described in the table below. Conversely, 12/25 had concordant HER2 status after NAC. Conclusions: At single center, the change in HER2 status after NAC with HP appeared frequent. Pathological review of additional cases is ongoing. The clinical significance is still unclear but may open the possibility to investigate tailored approach in post-neoadjuvant setting based on the biological profile of residual disease. [Table: see text]

Assessment of the knowledge level and experience of healthcare personnel concerning CPR and early defibrillation: an internal survey

Background

In‐hospital cardiac arrest (IHCA) is a major public health problem with significant mortality. Rapid cardiopulmonary resuscitation and early defibrillation is extremely connected to patient outcome. In this study, we aimed to assess the effects of a basic life support and defibrillation course in improving knowledge in IHCA management.

Methods

We performed a prospective observational study recruiting healthcare personnel working at Azienda Ospedaliero Universitaria Pisana, Pisa, Italy. Study consisted in the administration of two questionnaires before and after BLS-D course. The course was structured as an informative meeting and it was held according to European Resuscitation Council guidelines.

Results

78 participants completed pre- and post-course questionnaires. Only 31.9% of the participants had taken part in a BLS-D before our study. After the course, we found a significative increase in the percentage of participants that evaluated their skills adequate in IHCA management (17.9% vs 42.3%; p < 0.01) and in the correct use of defibrillator (38.8% vs 67.9% p < 0.001). However, 51.3% of respondents still consider their preparation not entirely appropriate after the course. Even more, we observed a significant increase in the number of corrected responses after the course, especially about sequence performed in case of absent vital sign, CPR maneuvers and use of defibrillator.

Conclusions

The training course resulted in significant increase in the level of knowledge about the general management of IHCA in hospital staff. Therefore, a simple intervention such as an informative meetings improved significantly the knowledge about IHCA and, consequently, can lead to a reduction of morbidity and mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02009-2.

TERT promoter hotspot mutations and gene amplification in metaplastic breast cancer

Metaplastic breast cancers (MBCs) are characterized by complex genomes, which seem to vary according to their histologic subtype. TERT promoter hotspot mutations and gene amplification are rare in common forms of breast cancer, but present in a subset of phyllodes tumors. Here, we sought to determine the frequency of genetic alterations affecting TERT in a cohort of 60 MBCs with distinct predominant metaplastic components (squamous, 23%; spindle, 27%; osseous, 8%; chondroid, 42%), and to compare the repertoire of genetic alterations of MBCs according to the presence of TERT promoter hotspot mutations or gene amplification. Forty-four MBCs were subjected to: whole-exome sequencing (WES; n = 27) or targeted sequencing of 341-468 cancer-related genes (n = 17); 16 MBCs were subjected to Sanger sequencing of the TERT promoter, TP53 and selected exons of PIK3CA, HRAS, and BRAF. TERT promoter hotspot mutations (n = 9) and TERT gene amplification (n = 1) were found in 10 of the 60 MBCs analyzed, respectively. These TERT alterations were less frequently found in MBCs with predominant chondroid differentiation than in other MBC subtypes (p = 0.01, Fisher's exact test) and were mutually exclusive with TP53 mutations (p < 0.001, CoMEt). In addition, a comparative analysis of the MBCs subjected to WES or targeted cancer gene sequencing (n = 44) revealed that MBCs harboring TERT promoter hotspot mutations or gene amplification (n = 6) more frequently harbored PIK3CA than TERT wild-type MBCs (n = 38; p = 0.001; Fisher's exact test). In conclusion, TERT somatic genetic alterations are found in a subset of TP53 wild-type MBCs with squamous/spindle differentiation, highlighting the genetic diversity of these cancers.

The genetic landscape of metaplastic breast cancers and uterine carcinosarcomas

Metaplastic breast carcinoma (MBC) and uterine carcinosarcoma (UCS) are rare aggressive cancers, characterized by an admixture of adenocarcinoma and areas displaying mesenchymal/sarcomatoid differentiation. We sought to define whether MBCs and UCSs harbor similar patterns of genetic alterations, and whether the different histologic components of MBCs and UCSs are clonally related. Whole-exome sequencing (WES) data from MBCs (n = 35) and UCSs (n = 57, The Cancer Genome Atlas) were reanalyzed to define somatic genetic alterations, altered signaling pathways, mutational signatures, and genomic features of homologous recombination DNA repair deficiency (HRD). In addition, the carcinomatous and sarcomatous components of an additional cohort of MBCs (n = 11) and UCSs (n = 6) were microdissected separately and subjected to WES, and their clonal relatedness was assessed. MBCs and UCSs harbored recurrent genetic alterations affecting TP53, PIK3CA, and PTEN, similar patterns of gene copy number alterations, and an enrichment in alterations affecting the epithelial-to-mesenchymal transition (EMT)-related Wnt and Notch signaling pathways. Differences were observed, however, including a significantly higher prevalence of FAT3 and FAT1 somatic mutations in MBCs compared to UCSs, and conversely, UCSs significantly more frequently harbored somatic mutations affecting FBXW7 and PPP2R1A as well as HER2 amplification than MBCs. Genomic features of HRD and biallelic alterations affecting bona fide HRD-related genes were found to be more prevalent in MBCs than in UCSs. The distinct histologic components of MBCs and UCSs were clonally related in all cases, with the sarcoma component likely stemming from a minor subclone of the carcinoma component in the samples with interpretable chronology of clonal evolution. Despite the similar histologic features and pathways affected by genetic alterations, UCSs differ from MBCs on the basis of FBXW7 and PPP2R1A mutations, HER2 amplification, and lack of HRD, supporting the notion that these entities are more than mere phenocopies of the same tumor type in different anatomical sites.

Immunohistochemical assessment of HRAS Q61R mutations in breast adenomyoepitheliomas

AIMS

Breast adenomyoepitheliomas (AMEs) are uncommon tumours. Most oestrogen receptor (ER)-positive AMEs have mutations in phosphoinositide 3-kinase (PI3K) pathway genes, whereas ER-negative AMEs usually harbour concurrent mutations affecting the HRAS Q61 hotspot and PI3K pathway genes. Here, we sought to determine the sensitivity and specificity of RAS Q61R immunohistochemical (IHC) analysis for detection of HRAS Q61R mutations in AMEs.

METHODS AND RESULTS

Twenty-six AMEs (14 ER-positive; 12 ER-negative) previously subjected to massively parallel sequencing (n = 21) or Sanger sequencing (n = 5) of the HRAS Q61 hotspot locus were included in this study. All AMEs were subjected to IHC analysis with a monoclonal (SP174) RAS Q61R-specific antibody, in addition to detailed histopathological analysis. Nine ER-negative AMEs harboured HRAS mutations, including Q61R (n = 7) and Q61K (n = 2) mutations. Five of seven (71%) AMEs with HRAS Q61R mutations were immunohistochemically positive, whereas none of the AMEs lacking HRAS Q61R mutations (n = 17) were immunoreactive. RAS Q61R immunoreactivity was restricted to the myoepithelium in 80% (4/5) of cases, whereas one case showed immunoreactivity in both the epithelial component and the myoepithelial component. RAS Q61R immunohistochemically positive AMEs were associated with infiltrative borders (P < 0.001), necrosis (P < 0.01) and mitotic index in the epithelial (P < 0.05) and myoepithelial (P < 0.01) components. RAS Q61R IHC assessment did not reveal Q61K mutations (0/2).

CONCLUSIONS

IHC analysis of RAS Q61R shows high specificity (100%) and moderate sensitivity (71%) for detection of HRAS Q61R mutations in breast AMEs, and appears not to detect HRAS Q61K mutations. IHC analysis of RAS Q61R may constitute a useful technique in the diagnostic workup of ER-negative AMEs.

Deep Multi-Magnification Networks for multi-class breast cancer image segmentation

Pathologic analysis of surgical excision specimens for breast carcinoma is important to evaluate the completeness of surgical excision and has implications for future treatment. This analysis is performed manually by pathologists reviewing histologic slides prepared from formalin-fixed tissue. In this paper, we present Deep Multi-Magnification Network trained by partial annotation for automated multi-class tissue segmentation by a set of patches from multiple magnifications in digitized whole slide images. Our proposed architecture with multi-encoder, multi-decoder, and multi-concatenation outperforms other single and multi-magnification-based architectures by achieving the highest mean intersection-over-union, and can be used to facilitate pathologists' assessments of breast cancer.

Interobserver Variation of PD-L1 SP142 Immunohistochemistry Interpretation in Breast Carcinoma: A Study of 79 Cases Using Whole Slide Imaging

CONTEXT.—

The Ventana programmed death ligand-1 (PD-L1) SP142 immunohistochemical assay (IHC) is approved by the US Food and Drug Administration as the companion diagnostic assay to identify patients with locally advanced or metastatic triple-negative breast cancer for immunotherapy with atezolizumab, a monoclonal antibody targeting PD-L1.

OBJECTIVE.—

To determine interobserver variability in PD-L1 SP142 IHC interpretation in invasive breast carcinoma.

DESIGN.—

The pathology database was interrogated for all patients diagnosed with primary invasive, locally recurrent, or metastatic breast carcinoma on which PD-L1 SP142 IHC was performed from November 2018 to June 2019 at our institution. A subset of cases was selected using a computerized random-number generator. PD-L1 IHC was evaluated in stromal tumor-infiltrating immune cells using the IMpassion130 trial criteria, with positive cases defined as immunoreactivity in immune cells 1% or more of the tumor area. IHC was interpreted on whole slide images by staff pathologists with breast pathology expertise. Interobserver variability was calculated using unweighted κ.

RESULTS.—

A total of 79 cases were assessed by 8 pathologists. Interobserver agreement was substantial (κ = 0.727). There was complete agreement among all 8 pathologists in 62% (49 of 79) of cases, 7 pathologists or more in 84% (66 of 79) of cases and 6 pathologists or more in 92% (73 of 79) of cases. In 4% (3 of 79) of cases, all of which were small biopsies, pathologists' interpretations were evenly split between scores of positive and negative.

CONCLUSIONS.—

The findings show substantial agreement in PD-L1 SP142 IHC assessment of breast carcinoma cases among 8 pathologists at a single institution. Further study is warranted to define the basis for discrepant results.

Accuracy of Magnetic Resonance Imaging-Guided Biopsy to Verify Breast Cancer Pathologic Complete Response After Neoadjuvant Chemotherapy: A Nonrandomized Controlled Trial

IMPORTANCE

After neoadjuvant chemotherapy (NAC), pathologic complete response (pCR) is an optimal outcome and a surrogate end point for improved disease-free and overall survival. To date, surgical resection remains the only reliable method for diagnosing pCR.

OBJECTIVE

To evaluate the accuracy of magnetic resonance imaging (MRI)-guided biopsy for diagnosing a pCR after NAC compared with reference-standard surgical resection.

DESIGN, SETTING, AND PARTICIPANTS

Single-arm, phase 1, nonrandomized controlled trial in a single tertiary care cancer center from September 26, 2017, to July 29, 2019. The median follow-up was 1.26 years (interquartile range, 0.85-1.59 years). Data analysis was performed in November 2019. Eligible patients had (1) stage IA to IIIC biopsy-proven operable invasive breast cancer; (2) standard-of-care NAC; (3) MRI before and after NAC, with imaging complete response defined as no residual enhancement on post-NAC MRI; and (4) definitive surgery. Patients were excluded if they were younger than 18 years, had a medical reason precluding study participation, or had a prior history of breast cancer.

INTERVENTIONS

Post-NAC MRI-guided biopsy without the use of intravenous contrast of the tumor bed before definitive surgery.

MAIN OUTCOMES AND MEASURES

The primary end point was the negative predictive value of MRI-guided biopsy, with true-negative defined as negative results of the biopsy (ie, no residual cancer) corresponding to a surgical pCR. Accuracy, sensitivity, positive predictive value, and specificity were also calculated. Two clinical definitions of pCR were independently evaluated: definition 1 was no residual invasive cancer; definition 2, no residual invasive or in situ cancer.

RESULTS

Twenty of 23 patients (87%) had evaluable data (median [interquartile range] age, 51.5 [39.0-57.5] years; 20 women [100%]; 13 White patients [65%]). Of the 20 patients, pre-NAC median tumor size on MRI was 3.0 cm (interquartile range, 2.0-5.0 cm). Nineteen of 20 patients (95%) had invasive ductal carcinoma; 15 of 20 (75%) had stage II cancer; 11 of 20 (55%) had ERBB2 (formerly HER2 or HER2/neu)-positive cancer; and 6 of 20 (30%) had triple-negative cancer. Surgical pathology demonstrated a pCR in 13 of 20 (65%) patients and no pCR in 7 of 20 patients (35%) when pCR definition 1 was used. Results of MRI-guided biopsy had a negative predictive value of 92.8% (95% CI, 66.2%-99.8%), with accuracy of 95% (95% CI, 75.1%-99.9%), sensitivity of 85.8% (95% CI, 42.0%-99.6%), positive predictive value of 100%, and specificity of 100% for pCR definition 1. Only 1 patient had a false-negative MRI-guided biopsy result (surgical pathology showed <0.02 cm of residual invasive cancer).

CONCLUSIONS AND RELEVANCE

This study's results suggest that the accuracy of MRI-guided biopsy to diagnose a post-NAC pCR approaches that of reference-standard surgical resection. MRI-guided biopsy may be a viable alternative to surgical resection for this population after NAC, which supports the need for further investigation.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03289195.

Papillary neoplasms of the breast including upgrade rates and management of intraductal papilloma without atypia diagnosed at core needle biopsy

Papillary neoplasms of the breast are a heterogeneous group of epithelial tumors nearly entirely composed of papillae. Their classification rests on the characteristics of the epithelium and the presence and distribution of the myoepithelial cells along the papillae and around the tumor. Papillary neoplasms of the breast can be diagnostically challenging, especially if only core needle biopsy (CNB) material is available. This review summarizes salient morphological and immunohistochemical features, clinical presentation, and differential diagnoses of papillary neoplasms of the breast. We include a contemporary appraisal of the upgrade rate to carcinoma (invasive carcinoma and ductal carcinoma in situ [DCIS]) and atypical hyperplasias in surgical excision specimens obtained following CNB diagnosis of papilloma without atypia, and a review of the available follow-up data in cases without immediate surgical excision.

Stromal MED12 exon 2 mutations in complex fibroadenomas of the breast

Aims

Here we explore the presence of mediator complex subunit 12 (MED12) exon 2 and telomerase reverse transcriptase (TERT) promoter hotspot mutations in complex fibroadenomas (CFAs) of the breast.

Methods

The stromal components from 18 CFAs were subjected to Sanger sequencing of MED12 exon 2 and the TERT promoter hotspot loci. The epithelial and stromal components of two MED12 mutated CFAs were subjected to laser capture microdissection, and Sanger sequencing of MED12 exon 2, TERT promoter and PIK3CA exons 9 and 20, separately.

Results

MED12 exon 2 mutations were identified in the stroma of 17% of CFAs. The analyses of epithelial and stromal components, microdissected separately, revealed that MED12 mutations were restricted to the stroma. No TERT promoter or PIK3CA mutations in exons 9 and 20 were detected in analysed CFAs.

Conclusions

Like conventional fibroadenomas, MED12 exon 2 mutations appear to be restricted to the stromal component of CFAs, supporting the notion that CFAs are stromal neoplasms.

MaTAR25 lncRNA regulates the Tensin1 gene to impact breast cancer progression

Misregulation of long non-coding RNA (lncRNA) genes has been linked to a wide variety of cancer types. Here we report on Mammary Tumor Associated RNA 25 (MaTAR25), a nuclear enriched and chromatin associated lncRNA that plays a role in mammary tumor cell proliferation, migration, and invasion, both in vitro and in vivo. MaTAR25 functions by interacting with purine rich element binding protein B (PURB), and associating with a major downstream target gene Tensin1 (Tns1) to regulate its expression in trans. The Tns1 protein product is a critical component of focal adhesions linking signaling between the extracellular matrix and the actin cytoskeleton. Knockout of MaTAR25 results in down-regulation of Tns1 leading to a reorganization of the actin cytoskeleton, and a reduction of focal adhesions and microvilli. We identify LINC01271 as the human ortholog of MaTAR25, and importantly, increased expression of LINC01271 is associated with poor patient prognosis and metastasis. Our findings demonstrate that LINC01271 represents a potential therapeutic target to alter breast cancer progression.

Whole-exome sequencing analysis of juvenile papillomatosis and coexisting breast carcinoma

Juvenile papillomatosis (JP) of the breast is a rare benign mass‐forming lesion occurring in young women, which is histologically characterized by a constellation of proliferative changes and large cysts, giving it the gross appearance of Swiss cheese. A subset of patients with JP report a family history of breast carcinoma and/or coexisting or subsequent breast carcinoma. We performed whole‐exome sequencing of the hyperplastic epithelial component of three JPs, including one with coexisting ductal carcinoma in situ (DCIS) and invasive ductal carcinoma of no special type (IDC‐NST). JPs harbored clonal somatic PIK3CA hotspot mutations in two cases. In the JP with coexisting DCIS and IDC‐NST, these lesions were clonally related to the associated JP, sharing a clonal PIK3CA E542K somatic hotspot mutation. JP showed a paucity of copy number alterations, whereas the associated DCIS and IDC‐NST showed concurrent 1q gains/16q losses, hallmarks of estrogen receptor (ER)‐positive breast cancers. We observed JP to harbor a dominant aging‐related mutational signature, whereas coexisting DCIS and IDC‐NST showed greater exposure to an APOBEC signature. Taken together, our findings suggest that, at least in a subset of cases, JP might constitute the substrate from which DCIS and invasive breast carcinomas develop.