The clinical behavior and genomic features of the so-called adenoid cystic carcinomas of the solid variant with basaloid features

Clinical Outcomes With Notch Inhibitors in Notch-Activated Recurrent/Metastatic Adenoid Cystic Carcinoma

BACKGROUND

Adenoid cystic carcinoma (ACC) with NOTCH-activating mutations presents a clinical challenge due to its poor prognosis. NOTCH inhibitors have emerged as a potential therapy for ACC patients with NOTCH activation. This study aimed to evaluate the efficacy of NOTCH inhibitors in this patient population.

METHODS

A retrospective analysis was conducted on patients with metastatic ACC harboring NOTCH pathway activation, who received NOTCH inhibitors at MD Anderson Cancer Center. NOTCH inhibitors included AL101, a gamma-secretase inhibitor, and brontictuzumab, an antibody targeting NOTCH1. NOTCH pathway activation was assessed through genomic analysis for NOTCH-activating mutations or immunohistochemistry for NOTCH1 intracellular domain (NICD1). Efficacy endpoints included best overall response (BOR) and progression-free survival (PFS) per RECIST or MD Anderson bone response criteria.

RESULTS

Twenty-nine patients were included, with a predominance of solid histology (86%). NOTCH-activating mutations were identified in 82% of patients, and 95% showed positive NICD1 staining. BOR revealed partial response in 17% of patients, stable disease in 55%, and progressive disease in 28%. Median response duration was longer for AL101 compared to brontictuzumab (9.9 vs. 1.7 months, p = 0.04). Median PFS with NOTCH inhibitor was 4.2 months (95% CI 2.7-8.6 months). Progression of nontarget lesions occurred in 34% of patients. Comparison with prior therapy showed longer PFS with NOTCH inhibitors (HR 0.38, 95% CI 0.19-0.78, p = 0.0065).

CONCLUSION

NOTCH inhibitors demonstrate activity in NOTCH-activated ACC, surpassing the efficacy of observation or prior systemic therapies. However, limited PFS and progression of nontarget lesions suggest the potential need for combination therapy to address ACC heterogeneity.

Solid basaloid adenoid cystic carcinoma of the breast: A high-grade triple negative breast carcinoma which rarely responds to neoadjuvant chemotherapy

Solid basaloid adenoid cystic carcinoma of the breast (SB-AdCC) is an exceedingly rare but important entity that warrants clear separation from classic AdCC (C-AdCC) for optimal treatment. This case series retrospectively reviewed the diagnosis and treatment of 20 breast AdCCs. While four breast pathologists reached consensus on the diagnosis of all C-AdCCs, there was considerable disagreement when diagnosing pure SB-AdCCs. The morphology and immunohistochemical profiles of SB-AdCC closely resemble those of basaloid triple-negative breast carcinoma (TNBC). Molecular profiling of SB-AdCC revealed frequent mutations in the Notch pathway and alterations in chromatin modifiers, such as CREBBP and KMT2D. MYB-NFIB fusion was rare and detected in only 2 of 9 (22.2 %) SB-AdCCs. Axillary lymph node metastasis was present in 2 of 10 patients with SB-AdCC at the time of surgery. During a median follow-up of 27 months, one patient with SB-AdCC developed axillary recurrence. Moreover, 6 of 12 (50.0 %) patients with SB-AdCC developed distant metastases. Of the three patients who underwent neoadjuvant chemotherapy for SB-AdCC, one achieved near-complete pathological response, while the remaining two had minimal response. In conclusion, this series underscores the aggressive clinical course of SB-AdCC, similar to conventional TNBC. Pathologically, SB-AdCC also closely mimics conventional TNBC. It is imperative for pathologists to clearly indicate C-AdCC or SB-AdCC or give a percentage of each component to ensure appropriate treatment strategies and avoid both over-treatment and under-treatment.

Primary pulmonary adenoid cystic carcinoma: A study of clinicopathological features and molecular alterations in twenty-one cases

BACKGROUND

Primary pulmonary adenoid cystic carcinoma (PACC) is a rare malignant tumor. Despite the growing sophistication of ACC research, scant studies have delved into the unique molecular alterations of ACC originating from the lung and the clinical features associations.

METHOD

Paraffin-embedded specimens of primary PACC tissues pathologically confirmed at the Affiliated Hospital of Qingdao University within the past decade were collected. We comprehensively evaluated the diversity of molecular alterations in PACC using immunohistochemistry (IHC) staining, fluorescence in-situ hybridization (FISH), and next-generation sequencing (NGS). Furthermore, the potential correlations between MYB rearrangement status and clinicopathological features were thoroughly analyzed.

RESULT

Twenty-one specimens of primary PACC were collected, including eighteen of the typical type and three of the solid-basaloid type. Fifteen (71.4 %) specimens exhibited positive MYB staining and MYB rearrangements. Notably, neither clinicopathological parameters nor MYB rearrangement predicted patients' overall survival (OS). However, MYB non-rearrangement was associated with a significantly higher rate of lymph node metastasis (75 % vs. 8.3 %, P = 0.027).

CONCLUSION

Investigating the heterogeneity and multimolecular characteristics of PACC based on different pathological types emerges as a potentially innovative strategy to pinpoint suitable candidates for targeted therapies.

Unraveling complexity and leveraging opportunities in uncommon breast cancer subtypes

Special histologic subtypes of breast cancer (BC) exhibit unique phenotypes and molecular profiles with diagnostic and therapeutic implications, often differing in behavior and clinical trajectory from common BC forms. Novel methodologies, such as artificial intelligence may improve classification. Genetic predisposition plays roles in a subset of cases. Uncommon BC presentations like male, inflammatory and pregnancy-related BC pose challenges. Emerging therapeutic strategies targeting genetic alterations or immune microenvironment are being explored.

Molecular Basis of Breast Tumor Heterogeneity

Breast cancer (BC) is a profoundly heterogenous disease, with diverse molecular, histological, and clinical variations. The intricate molecular landscape of BC is evident even at early stages, illustrated by the complexity of the evolution from precursor lesions to invasive carcinoma. The key for therapeutic decision-making is the dynamic assessment of BC receptor status and clinical subtyping. Hereditary BC adds an additional layer of complexity to the disease, given that different cancer susceptibility genes contribute to distinct phenotypes and genomic features. Furthermore, the various BC subtypes display distinct metabolic demands and immune microenvironments. Finally, genotypic-phenotypic correlations in special histologic subtypes of BC inform diagnostic and therapeutic approaches, highlighting the significance of thoroughly comprehending BC heterogeneity.

[Fusion genes in salivary gland tumors]

Salivary gland tumors represent a diagnostic challenge for pathologists due to their rarity, their very wide histopathological and immuno-phenotypic spectrum, and the recent identification of new entities. This article presents the main molecular characteristics of these tumors in order to allow any pathologist to perceive the diagnostic tracks of these ENT tumors and to better guide the molecular approach to establish the diagnosis and guide therapy.

Salivary gland-like tumors of the breast: Histopathologic and genetic features with clinical implications

Salivary gland-like tumors of the breast are rare neoplasms that share morphologic, immunophenotypic, and/or genetic features with their salivary gland counterparts, highlighting a shared underlying histopathogenesis in most cases. Salivary gland-like carcinomas included in the World Health Organization classification of breast tumors are adenoid cystic carcinoma, secretory carcinoma, mucoepidermoid carcinoma, acinic cell carcinoma, and the exceedingly rare polymorphous adenocarcinoma. These carcinomas are usually triple negative for estrogen receptor and progesterone receptor expression and HER2 overexpression, yet generally have favorable prognosis, in contrast to high-grade triple negative carcinomas of no special type. On the other hand, a small subset, such as solid-basaloid adenoid cystic carcinoma, rare high-grade carcinomas, and those associated with transformation to other types of high-grade invasive carcinoma can behave more aggressively. Other salivary gland-like tumors of the breast, such as pleomorphic adenoma and adenomyoepithelioma, are usually benign but can rarely undergo malignant transformation. Although clinical experience with salivary gland-like breast tumors is overall limited, their recognition and accurate classification has important implications for prognosis and clinical management, especially to avoid overtreatment of salivary gland-like carcinomas. The identification of characteristic genetic alterations and/or immunohistochemical surrogates in many of these tumors has practical applications to establishing an accurate diagnosis and directing clinical management. This review highlights the histopathologic and genetic characteristics of salivary gland-like breast tumors and the implications of the diagnosis for current clinical management.

Impact of NOTCH1 expression in primary breast adenoid cystic carcinoma

AIMS

Adenoid cystic carcinoma (AdCC) originates from salivary-type like glands in the head and neck, lung, and breast. AdCC shows chromosomal translocation, resulting in MYB::NFIB fusion and overexpression of MYB. Recently, NOTCH1 pathway alteration has been recognised in a subset of patients with salivary gland AdCC and has been shown to be associated with poor survival. In this study, we investigated the correlation of NOTCH1 pathway alteration with the clinical outcome of patients with primary breast AdCC by examining NOTCH1 immunoreactivity in attempts to better predict clinical outcomes.

METHODS

We identified 25 cases of breast AdCC, reviewed the clinical outcome and performed immunohistochemical (IHC) staining for NOTCH1 on FFPE sections.

RESULTS

IHC evaluation of NOTCH1 expression in 25 cases of primary breast AdCCs revealed a positive correlation between NOTCH1 expression and primary tumour size. All cases with NOTCH1 expression were greater than 15 mm in size at presentation but only 50% of NOTCH1 negative tumours were greater than 15 mm. We demonstrated a positive correlation between NOTCH1 positive AdCCs and recurrence/metastases. 63.6% of NOTCH1 positive AdCCs had either metastases or recurrence. On the contrary, only 21.5% of NOTCH1 negative AdCCs had recurrence or metastases. AdCCs with NOTCH1 positivity correlated with inferior relapse free survival (median 33 vs 129 months).

CONCLUSIONS

Our study demonstrates that in patients with breast AdCC, overexpression of NOTCH1 ≥20% is associated with larger tumour size and aggressive clinical outcomes. Importantly, NOTCH1 inhibitors may have potential therapeutic effect in patients with breast AdCC.

Molecular pathology in breast disease: diagnostic, prognostic, and therapeutic tools

Molecular testing in breast cancer gained increasing attention and importance as specific molecular results can tailor not only oncological decisions on systemic adjuvant or neoadjuvant or in metastatic setting, but increasingly serve in diagnostic routine histopathological services to differentiate between morphologically overlapping or ambiguous histological pictures. Diagnostic tools involve in most cases a broad spectrum of immunohistochemical panels, followed by entity-specific in situ hybridization probes and in given cases NGS-based sequencing. Workflow of which methodology is applied and in which order depends on the specific entity resp. on the given differential diagnosis in question. Regarding prognostic/predictive molecular testing, the choice of assay and the workflow are based on clinical algorithms and on the evidence of targeted therapies following the molecular alterations. In this review paper, we aim to address the use of molecular technics in [1] the histological diagnostic setting (such as subtyping of invasive carcinomas/malignant spindle cell tumors and sarcomas and some B3 lesions) and [2] in the context of adjuvant or neoadjuvant or other clinical settings with special focus of targeted therapies.

Solid basal adenoid cystic carcinoma of the breast: A case report and literature review

RATIONALE

Adenoid cystic carcinoma (AdCC) is a rare malignancy of the breast with a low Ki-67 index and good prognosis. Owing to the rarity of breast AdCC, the misdiagnosis rate is as high as 50%, and there is no consensus or recognized guidelines for the treatment of this disease. Therefore, it is necessary to conduct a detailed clinical and pathological analysis in combination with a literature review to improve our understanding, diagnosis, and treatment of the disease.

METHODS

A 68-year-old woman sought medical attention due to a recently increasing mass in the breast. The left breast mass was 1.3 cm × 1 cm in size. We analyzed the morphology, immunohistochemistry, and molecular characteristics of the tumor removed by surgery, and reviewed relevant literature.

DIAGNOSES

Solid basal AdCC of the breast.

INTERVENTIONS

We performed biopsy, immunohistochemistry and molecular testing on surgical resection specimens.

OUTCOMES

Combining morphological and immunohistochemical features, it is consistent with solid basal AdCC of the breast, and Fish detected MYB gene break.

LESSONS

Due to the high misdiagnosis rate of AdCC, accurate histopathological diagnosis is particularly important. At present, breast conserving surgery and local tumor resection are mainly used for the treatment of breast AdCC, and postoperative adjuvant radiotherapy is feasible.

Solid-Basaloid Adenoid Cystic Carcinoma of the Breast: An Aggressive Subtype Enriched for Notch Pathway and Chromatin Modifier Mutations With MYB Overexpression

Adenoid cystic carcinoma (AdCC) is a rare triple-negative breast cancer analogous to its extramammary counterparts. Diagnosis of the more aggressive solid-basaloid variant of AdCC (SB-AdCC) can be challenging due to poorly defined histopathologic and molecular features. We characterized 22 invasive and in situ basaloid carcinomas by morphology, immunohistochemistry, genetics, and MYB status using multiple platforms and assessed clinical behavior and neoadjuvant chemotherapy responses. After consensus review, 16/22 cases were classified as SB-AdCC. All SB-AdCC had predominantly solid growth and at least focal myxohyaline stroma and were immune-poor. Eosinophilic squamoid cells (69%, 11/16) and basement membrane-like secretions (69%, 11/16) were common, and intercalated ducts (31%, 5/16) were less frequent. SB-AdCC typically expressed SOX10 (100%, 16/16) and luminal markers (100%, 16/16 CK7; 88%, 14/16 CD117; 93%, 13/14 CAM5.2). SMA (40%, 6/15) expression was less common, and SMM (27%, 3/11), GATA3 (20%, 3/15), and p63 (25%, 4/16) were mostly negative. MYB protein and/or MYB RNA overexpression was universal in evaluable cases (13/13), with RNA in situ hybridization (10/10) more reliable than immunohistochemistry (10/11, plus 4 excisions inconclusive). Fluorescence in situ hybridization and/or next-generation sequencing identified MYB rearrangements (20%, 3/15) and amplifications/copy gains (60%, 9/15) but no MYB::NFIB fusions. SB-AdCC often had aberrations in Notch pathway (60%, including 40% NOTCH1 and 20% NOTCH2) and/or chromatin modifier (60%, including 33% CREBBP) genes, with relatively infrequent TP53 mutations (27%). Unclassified invasive basaloid carcinomas lacking described histologic features of SB-AdCC (n = 4) and basaloid ductal carcinoma in situ (n = 2) showed similar immunoprofiles and genetics as SB-AdCC, including Notch aberrations and MYB overexpression with MYB rearrangements/amplifications. Overall, nodal (22%) and distant (33%) metastases were common, and 23% of patients died of disease (mean follow-up, 35 months; n = 22). Responses were poor in all 7 neoadjuvant chemotherapy-treated patients, without any achieving pathologic complete response. The data highlight the histopathologic spectrum of basaloid carcinomas including SB-AdCC and reveal shared genetics and MYB activation, which can be diagnostically useful. Aggressive behavior and poor treatment responses emphasize a need for additional treatment approaches.

The Role of Novel Immunohistochemical Markers for Special Types of Breast Carcinoma

Some histologic special types of breast carcinoma harbor specific recurrent genetic alterations that are not seen in other types of breast carcinoma (no special type), namely adenoid cystic carcinoma, secretory carcinoma, and tall cell carcinoma with reversed polarity. These tumors have unique morphologic features, are triple-negative, that is, do not express hormone receptors or HER2, and are generally associated with a favorable prognosis. Adenoid cystic carcinoma, like its counterpart in other organs, shows a MYB-NFIB fusion gene that is the result of a recurrent t(6;9)(q22-23;p23-24) translocation. Other MYB alterations have been described that result in overexpression of MYB . Secretory carcinoma is characterized by an ETV6-NTRK3 gene fusion that is the result of recurrent (12;15);(p13;q25) translocation, which is also seen in mammary analog secretory carcinoma of the salivary gland. Tall cell carcinoma with reversed polarity shows IDH2 p.Arg172 hotspot mutations. Immunohistochemical antibodies have emerged that identify the underlying genetic alterations in these tumors and serve as useful diagnostic tools. This review will provide an update on the molecular features and diagnostic immunohistochemical markers that have become increasingly popular to aid in diagnosing these uncommon triple-negative breast tumors.

A novel EWSR1-MYB fusion in an aggressive advanced breast adenoid cystic carcinoma with mixed classical and solid-basaloid components

Breast adenoid cystic carcinoma (AdCC) with a solid-basaloid component is rare. The solid-basaloid component is usually characterized by solid nests composed of basal-like cells with marked nuclear atypia, high mitotic activity, and necrosis. Given the rarity of such tumors, information on their clinicopathological and genomic characteristics is limited. Herein, we report a case of advanced breast cancer with a poor prognosis with histological and immunohistochemical characteristics of AdCC with a solid-basaloid component. For the solid-basaloid component, fluorescence in situ hybridization (FISH) analysis revealed rearrangement of the EWSR1 and MYB genes, and immunohistochemical staining indicated MYB positivity. Next-generation sequencing-based technology revealed a novel EWSR1-MYB fusion. To our knowledge, this is the first report of an EWSR1-MYB fusion in AdCC with a solid-basaloid component and a poor prognosis. Our findings may extend the genetic understanding of AdCC and aid in the clinical diagnosis of AdCC.

Detection of salivary gland and sinonasal fusions by a next-generation sequencing based, ligation-dependent, multiplex RT-PCR assay

AIMS

The discovery of tumour type-specific gene fusion oncogenes in benign and malignant salivary gland and sinonasal (SGSN) tumours has significantly increased our knowledge about their molecular pathology and classification.

METHODS AND RESULTS

We developed a new targeted multiplexed next-generation sequencing (NGS)-based method that utilizes ligation dependent reverse-transcriptase polymerase chain reaction (LD-RT-PCR) to detect oncogenic fusion transcripts involving 116 genes, leading to 96 gene fusions known to be recurrently rearranged in these tumours. In all, 180 SGSN tumours (formalin-fixed, paraffin-embedded samples, 141 specimens and 39 core needle biopsies) from the REFCORpath (French network for rare head and neck cancers) with previously identified fusion genes by fluorescent in situ hybridisation (FISH), RT-PCR, or molecular immunohistochemistry were selected to test its specificity and sensitivity and validate its diagnostic use. Tested tumours encompassed 14 major tumours types, including secretory carcinoma, mucoepidermoid carcinoma, adenoid cystic carcinoma, salivary gland intraductal carcinoma, clear cell carcinoma, pleomorphic adenoma, adamantinoma-like Ewing Sarcoma, EWSR1::COLCA2 sinonasal sarcoma, DEK::AFF2 sinonasal carcinoma, and biphenotypic sinonasal sarcoma. In-frame fusion transcripts were detected in 97.8% of cases (176/180). Gene fusion assay results correlated with conventional techniques (immunohistochemistry [IHC], FISH, and RT-PCR) in 176/180 tumours (97.8%).

CONCLUSION

This targeted multiplexed NGS-based LD-RT-PCR method is a robust, highly sensitive method for the detection of recurrent gene fusions from routine clinical SGSN tumours. It can be easily customized to cover new fusions. These results are promising for implementing an integrated NGS system to rapidly detect genetic aberrations, facilitating accurate, genomics-based diagnoses, and accelerate time to precision therapies in SGSN tumours.

The Landscape of MYB/MYBL1- and Peri-MYB/MYBL1-Associated Rearrangements in Adenoid Cystic Carcinoma

Approximately 60% of adenoid cystic carcinoma (AdCC) cases are positive for MYB::NFIB or MYBL1::NFIB, whereas MYB/MYBL1 oncoprotein, a key driver of AdCC, is overexpressed in most cases. Juxtaposition of superenhancer regions in NFIB and other genes into the MYB/MYBL1 locus is an attractive oncogenic hypothesis for AdCC cases, either negative or positive for MYB/MYBL1::NFIB. However, evidence supporting this hypothesis is insufficient. We examined 160 salivary AdCC cases for rearrangements in MYB/MYBL1 loci and peri-MYB/MYBL1 areas (centromeric and telomeric areas of 10 Mb each) using formalin-fixed, paraffin-embedded tumor sections. For the detection of the rearrangements, we employed conventional fluorescence in situ hybridization split and fusion assays and a 5 Mb fluorescence in situ hybridization split assay. The latter is a novel assay that enabled us to detect any possible splits within a 5 Mb distance of a chromosome. We found MYB/MYBL1- and peri-MYB/MYBL1-associated rearrangements in 149/160 patients (93%). AdCC cases positive for rearrangements in MYB, MYBL1, the peri-MYB area, and the peri-MYBL1 area numbered 105 (66%), 20 (13%), 19 (12%), and 5 (3%), respectively. In 24 peri-MYB/MYBL1 rearrangement-positive cases, 14 (58%) were found to have a juxtaposition of the NFIB or RAD51B locus into the MYB/MYBL1 loci. On comparing with a tumor group positive for MYB::NFIB, a hallmark of AdCC, other genetically classified tumor groups had similar features of overexpression of the MYB transcript and MYB oncoprotein as detected by semiquantitative RT-qPCR and immunohistochemistry, respectively. In addition, clinicopathological and prognostic features were similar among these groups. Our study suggests that peri-MYB/MYBL1 rearrangements may be a frequent event in AdCC and may result in biological and clinicopathological consequences comparable to MYB/MYBL1 rearrangements. The landscape of MYB/MYBL1 and peri-MYB/MYBL1 rearrangements shown here strongly suggests that juxtaposition of superenhancers into MYB/MYBL1 or peri-MYB/MYBL1 loci is an alteration that acts as a key driver for AdCC oncogenesis and may unify MYB/MYBL1 rearrangement-positive and negative cases.

Molecular Classification of Breast Cancer

Breast carcinomas classified based on traditional morphologic assessment provide useful prognostic information. Although morphology is still the gold standard of classification, recent advances in molecular technologies have enabled the classification of these tumors into four distinct subtypes based on its intrinsic molecular profile that provide both predictive and prognostic information. This article describes the association between the different molecular subtypes with the histologic subtypes of breast cancer and illustrates how these subtypes may affect the appearance of tumors on imaging studies.

Salivary Gland-like Tumors of the Breast

CONTEXT

The World Health Organization classification of tumors of the breast recognizes several special type carcinomas and benign lesions with features comparable to those of salivary gland tumors.

OBJECTIVE

To discuss the histologic, immunophenotypic, molecular, and clinical features of salivary gland-like carcinomas of the breast. These breast tumors are often negative for hormone receptors and human epidermal growth factor receptor 2 (HER2), that is, triple-negative, but they generally have a much better prognosis than triple-negative breast carcinomas of no special type. We compare the immunophenotypic, molecular, and clinical features of these breast tumors with their salivary gland counterparts, highlighting similarities and differences. We also discuss benign salivary gland-like breast tumors. Finally, we highlight recent developments in understanding the molecular pathogenesis of these breast tumors and novel ancillary studies that can be used to support their diagnosis.

DATA SOURCES

A literature review was conducted, and papers were selected for further analysis and discussion by the authors of this review based on their novelty, applicability, and impact in the field.

CONCLUSIONS

Breast tumors that exhibit morphologic overlap with salivary gland tumors have been recognized by pathologists for decades, but the similarities and differences in their molecular pathogenesis have not been understood until more recently. These developments have led to novel diagnostic tools and further knowledge of these rare breast lesions.

Rare subtypes of triple negative breast cancer: Current understanding and future directions

Rare subtypes of triple-negative breast cancers (TNBC) are a heterogenous group of tumors, comprising 5-10% of all TNBCs. Despite accounting for an absolute number of cases in aggregate approaching that of other less common, but well studied solid tumors, rare subtypes of triple-negative disease remain understudied. Low prevalence, diagnostic challenges and overlapping diagnoses have hindered consistent categorization of these breast cancers. Here we review epidemiology, histology and clinical and molecular characteristics of metaplastic, triple-negative lobular, apocrine, adenoid cystic, secretory and high-grade neuroendocrine TNBCs. Medullary pattern invasive ductal carcinoma no special type, which until recently was a considered a distinct subtype, is also discussed. With this background, we review how applying biological principals often applied to study TNBC no special type could improve our understanding of rare TNBCs. These could include the utilization of targeted molecular approaches or disease agnostic tools such as tumor mutational burden or germline mutation-directed treatments. Burgeoning data also suggest that pathologic response to neoadjuvant therapy and circulating tumor DNA have value in understanding rare subtypes of TNBC. Finally, we discuss a framework for advancing disease-specific knowledge in this space. While the conduct of randomized trials in rare TNBC subtypes has been challenging, re-envisioning trial design and technologic tools may offer new opportunities. These include embedding rare TNBC subtypes in umbrella studies of rare tumors, retrospective review of contemporary trials, prospective identification of patients with rare TNBC subtypes entering on clinical trials and querying big data for outcomes of patients with rare breast tumors.

Breast Cancer Pathology in the Era of Genomics

The era of genomic medicine provides an opportunity for pathologists to offer greater detail about the molecular underpinnings of a patient's cancer and thereby more targeted therapeutic options. In this review article, the role of genomics in breast cancer pathology is discussed, as it pertains to risk management, classification of special tumor types, predictive and prognostic testing, identification of actionable therapeutic targets, and monitoring for disease progression or development of treatment resistance.

Clinicopathologic Predictors of Clinical Outcomes in Mammary Adenoid Cystic Carcinoma: A Multi-institutional Study

Adenoid cystic carcinoma (AdCC) is an uncommon type of invasive breast carcinoma with a favorable prognosis. However, some cases are aggressive. The study aims to define the clinicopathologic predictors of outcome. Clinical, radiological, and pathologic variables were recorded for 76 AdCC cases from 11 institutions. The following histologic characteristics were evaluated by the breast pathologist in each respective institution, including Nottingham grade (NG), percentages of various growth patterns (solid, cribriform, trabecular-tubular), percentage of basaloid component, tumor borders (pushing, infiltrative), perineural invasion, lymphovascular invasion, necrosis, and distance from the closest margin. Various grading systems were evaluated, including NG, salivary gland-type grading systems, and a new proposed grading system. The new grading system incorporated the growth pattern (percent solid, percent cribriform), percent basaloid morphology, and mitotic count using the Youden index criterion. All variables were correlated with recurrence-free survival. Nineteen (25%) women developed local and/or distant recurrence. Basaloid morphology (≥25% of the tumor) was identified in 20 (26.3%) cases and a solid growth pattern (using ≥60% cutoff) in 22 (28.9%) cases. In the univariate analysis, the following variables were significantly correlated with worse recurrence-free survival: solid growth pattern, basaloid morphology, lymphovascular invasion, necrosis, perineural invasion, and pN-stage. In the multivariate analysis including basaloid morphology, pN-stage, lymphovascular invasion, and perineural invasion, basaloid morphology was statistically significant, with a hazard ratio of 3.872 (95% CI, 1.077; 13.924; P =.038). The NG and the new grading system both correlated with recurrence-free survival. However, grade 2 had a similar risk as grade 3 in the NG system and a similar risk as grade 1 in the new grading system. For solid growth patterns and basaloid morphology, using a 2-tier system with 1 cutoff was better than a 3-tier system with 2 cutoffs. Basaloid morphology and solid growth pattern have prognostic values for AdCC, with a 2-tier grading system performing better than a 3-tier system.

Breast lesions with myoepithelial phenotype

Myoepithelial cells (MECs) constitute a continuous layer of cells surrounding the breast glands, localised between the epithelial cells (ECs) and the basal membrane. MECs play important roles in normal mammary gland as they produce basal membrane and stimulate secretion. During neoplastic transformation, MECs act as a barrier preventing stromal invasion. MECs themselves can undergo a great variety of changes, ranging from hyperplastic to metaplastic, to neoplastic, and giving rise to a wide spectrum of morphological pictures sometimes difficult to interpret on routine diagnoses. Several benign and malignant breast tumours can present features of MECs differentiation. As these latter tumours are quite infrequent, the purpose of the present study is to offer a review of the morphological spectrum of MECs lesions, with correlations to prognosis.

Adenoid Cystic Carcinoma of the Breast: Radiologic-Pathologic Correlation

Adenoid cystic carcinoma (ACC) is an uncommon malignancy occurring most frequently in the salivary glands. Breast ACC is rare. Pain is common at the site of ACC; otherwise, presentation is similar to other primary breast cancers. Adenoid cystic carcinomas classically lack calcifications; the imaging manifestations of ACC are otherwise highly variable, likely related to multiple pathologic growth patterns. While ACC in other regions of the body tends to be more aggressive, ACC involving the breast typically has less aggressive biologic characteristics. Classic-type breast ACC has a lower tendency to recur locally with radiation, metastasize to regional lymph nodes, and spread to other parts of the body. Perineural spread of disease can be seen but is not common. The rarer solid basaloid-type has a higher tendency for local or distant spread and recurrence. Although ACC is usually triple receptor-negative (estrogen receptor, progesterone receptor, human epidermal growth factor-2 receptor), the indolent nature of this tumor dictates its management. With classic-type ACC, the inclusion of axillary surgery has no consensus and the use of chemotherapy or hormonal therapy is rare. Axillary nodal surgery and chemotherapy are often included in management of the more aggressive solid basaloid-type. An understanding of the breast imaging, histopathology, and clinical course is key for appropriate treatment and follow-up of ACC.

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.

Adenoid Cystic Carcinoma, Solid-Basaloid Subtype of the Breast: A Case Report

We present a rare tumor of adenoid cystic carcinoma, solid-basaloid subtype of the breast. Solid-basaloid adenoid cystic carcinoma may have a worse prognosis than classical adenoid cystic carcinoma. A 70-year-old woman presented with a mass in her left breast. Malignancy was suspected on imaging and confirmed via core needle biopsy. Left breast partial mastectomy and sentinel lymph node biopsy were performed. Histologically, the tumor was composed of basaloid cells with hyperchromatic nuclei and frequent mitotic figures, as are small-cell neuroendocrine carcinomas. Immunohistochemical analysis of the tumor cells showed high expression of KIT and CD10 and focal expression of keratin 7. Synaptophysin, chromogranin A, estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 were not expressed. This patient should be followed up carefully for distant metastases and recurrences.

Distinct clinicopathological and genomic features in solid and basaloid adenoid cystic carcinoma of the breast

Adenoid cystic carcinoma (AdCC) of the breast is a rare indolent carcinoma of salivary gland-type tumors, frequently associated with MYB genetic alteration. Solid and basaloid adenoid cystic carcinoma (SB-AdCC) is considered a sparse variant of AdCC. This study sought to search for clinicopathological and genomic features in SB-AdCC. Registered clinicopathological data on a cohort of 13 AdCC of the breast cases, including six conventional adenoid cystic carcinoma (C-AdCC) cases and seven SB-AdCC cases, were collected. MYB gene rearrangement via fluorescent in situ hybridization was investigated and MYB protein expression was evaluated by immunohistochemistry. Compared with C-AdCC, we found that the distribution of SB-AdCC cases were shifted to older age and were more frequently distant metastasis. Moreover, metastasis cases also showed a high (exceed 30%) Ki-67 index. Both groups showed MYB rearrangements and MYB protein expression, but they were less frequent in SB-AdCC than C-AdCC. To conclude, our results suggest that SB-AdCC is an aggressive variant of mammary AdCC with a higher incidence of distant metastases compared with C-AdCC, though they share common molecular features. A high Ki-67 index may be an adverse prognostic factor for metastasis.