E-cadherin immunohistochemistry in breast pathology: uses and pitfalls

Aberrant E-cadherin Expression in Lobular Carcinoma In Situ: A Comprehensive Immunohistochemical Evaluation of N-terminal, Extracellular, and C-terminal E-cadherin Domains

E-cadherin (E-cad) immunohistochemistry is commonly used to distinguish lobular carcinoma in situ (LCIS) from ductal carcinoma in situ in histologically uncertain or ambiguous cases. Although most LCIS cases show an absence of E-cad expression on the neoplastic cell membranes, some show aberrant E-cad expression which can lead to diagnostic confusion. Awareness and understanding of the frequency, patterns, and distribution of aberrant E-cad staining in LCIS is crucial to achieving a correct diagnosis. We studied 55 LCIS cases diagnosed on core needle biopsy, classified each case by WHO subtype (classic, pleomorphic, or florid), and evaluated the frequency and patterns of aberrant E-cad expression using 3 different E-cad antibodies targeting the N-terminal (N), extracellular (EC), and C-terminal domains (C). Aberrant E-cad expression in one or more of the E-cad domains was identified in 17 cases (31%) and was significantly more frequent among LCIS variants (10/19, 56%) than among classic cases (7/36, 19.4%) ( P =0.02). Among these 17 cases, aberrant E-cad expression was seen for all 3 domains in 10 cases, for EC+C in 4, for EC+N in 2, and for N only in 1. These results indicate that about one-third of cases of LCIS can show aberrant E-cad expression, that this is more common in variants than classic types of LCIS, and that this may be seen in different E-cad domains, most often in combination. These different patterns of aberrant E-cad expression may reflect different mechanisms of E-cad alterations in LCIS, the underlying nature of which merits further studies.

Non-invasive Lobular Neoplasia: Review and Updates

Non-invasive lobular neoplasia (LN) encompasses atypical lobular hyperplasia (ALH), classic lobular carcinoma in situ (CLCIS), florid lobular carcinoma in situ (FLCIS), and pleomorphic lobular carcinoma in situ (PLCIS). Lobular neoplasia is a neoplastic epithelial proliferation of the terminal duct lobular unit. A defining feature is discohesion due to the loss of E-cadherin, a protein that facilitates cell-to-cell adhesion. Lobular neoplasia is both a risk factor and a non-obligate precursor of invasive breast carcinoma. Classic LN, characterized by small, non-cohesive monomorphic cells, includes ALH and classic LCIS. While classic LN is usually not seen on imaging and, therefore, is diagnosed incidentally, FLCIS and PLCIS are typically the imaging targets, most often manifesting as calcifications. Unlike classic LN, which is typically hormone receptor-positive and HER2-negative, FLCIS and PLCIS may present with less favorable phenotypes. While ALH and CLCIS diagnosed on concordant core biopsy are generally managed with surveillance with or without chemoprevention, complete surgical excision is recommended for FLCIS and PLCIS due to high upgrade rates to invasive carcinoma. Accurate classification of non-invasive breast neoplastic lesions is essential for guiding treatment. This review provides an overview of the clinical features, pathology, and management of lobular neoplasia, emphasizing the importance of accurate diagnosis and individualized patient care.

E-cadherin staining in the diagnosis of lobular versus ductal neoplasms of the breast: the emperor has no clothes

Categorizing breast neoplasia as ductal or lobular is a daily exercise that relies on a combination of histologic and immunohistochemical tools. The historically robust link between loss of the E-cadherin molecule and lobular neoplasia has rendered staining for E-cadherin by immunohistochemistry a staple of this diagnostic process. Unfortunately, discordances between E-cadherin expression and histomorphology, and variations in E-cadherin staining patterns and intensities abound in clinical practice, but are often neglected in favour of a binary interpretation of the E-cadherin result. In this article, we highlight the complexities of E-cadherin expression through a review of the E-cadherin protein and its associated gene (CDH1), the mechanisms leading to aberrant/absent E-cadherin expression, and the implications of these factors on the reliability of the E-cadherin immunohistochemical stain in the classification of ductal versus lobular mammary neoplasia.

Unique Molecular Alteration of Lobular Breast Cancer: Association with Pathological Classification, Tumor Biology and Behavior, and Clinical Management

Invasive lobular carcinoma (ILC), accounting for up to 15% of diagnosed breast cancers, has garnered significant attention due to the loss of the epithelial cell-cell adhesion molecule E-cadherin. This loss contributes to its distinct biological, morphological, and clinical characteristics compared to non-lobular breast cancers. The use of immunohistochemistry (IHC) for E-cadherin and/or the associated cadherin-catenin complex, such as p120-catenin and beta-catenin, in morphologically equivocal cases, has been increasingly adopted in pathology practice. This approach has substantially improved diagnostic accuracy, interobserver reproducibility, and the identification of new morphologic variants of ILC. ILCs exhibit unique tumor biology, which presents considerable challenges in clinical management, especially in preoperative imaging evaluation, surgical management, and neoadjuvant treatment. Recent advances in translational and clinical research have enhanced our understanding of ILC and have spurred the development of new clinical trials specifically targeting these cancers. This review highlights recent progress in various aspects of ILC, including its unique molecular alteration, pathological classification and diagnostic approach, tumor biology and behavior, key clinical management challenges, and ongoing clinical trials, as well as the role of artificial intelligence in diagnosing ILC radiologically and pathologically. The goal of this review is to provide an updated understanding of the tumor biology, clinical manifestations, and molecular landscape of ILC and to help refine current tumor classification and diagnosis, subsequently improving management strategies and overall outcomes for lobular carcinoma patients.

Comprehensive characterization of invasive mammary carcinoma with lobular features: integrating morphology and E-cadherin immunohistochemistry patterns

BACKGROUND

Breast cancer treatment prioritizes molecular subtypes over histologic types. However, considering the unique biological behavior of invasive lobular carcinoma (ILC), its diagnosis is crucial for patient management. Therefore, this study aimed to review breast cancer cases, focusing on the E-cadherin patterns and lobular morphology of cases misclassified in the original reports.

METHODS

A comprehensive review was conducted on 481 breast cancer biopsy cases diagnosed as invasive breast carcinoma of no special type (IBC-NST) or ILC with E-cadherin staining. These cases were categorized into six groups based on tumor morphology (ductal/lobular) and E-cadherin expression pattern (membranous/loss/aberrant): (1) ductal/membranous, (2) lobular/loss, (3) lobular/aberrant, (4) mixed, (5) ductal/loss or aberrant, and (6) lobular/membranous.

RESULTS

In 211 cases (43.8%), an E-cadherin pattern indicating ILC (loss and aberrant) was observed alongside lobular morphology, representing 5.52% of all breast cancer biopsies during the relevant period. Moreover, 181 cases (37.6%) showed a membranous pattern with ductal morphology, 4 (0.8%) were mixed IBC-NST and ILC, and 85 (17.7%) exhibited discordance between morphology and E-cadherin expression. Notably, only 25.9% (15/58) of cases in group 3, characterized by aberrant E-cadherin patterns, were initially diagnosed as ILC, highlighting a significant diagnostic discrepancy. In group 6, where membranous E-cadherin pattern was present with lobular morphology, only 3.4% (2/58) were diagnosed as ILC in the original reports, indicating diagnostic challenges in morphology and immunohistochemistry discordance. Similarly, in group 5, which had ductal morphology with loss or aberrant E-cadherin expression, the initial diagnosis rate of IBC-NST was 33.3% (9/27), reflecting the complexities in interpreting discordant cases.

CONCLUSIONS

In real-world practice, diagnosing ILC often heavily depends on E-cadherin results. This study emphasizes the need for diagnostic clarification in cases with discordance between morphology and E-cadherin patterns.

Prediction of High Nodal Burden in Patients With Sentinel Node-Positive Luminal ERBB2-Negative Breast Cancer

Importance

In patients with clinically node-negative (cN0) breast cancer and 1 or 2 sentinel lymph node (SLN) macrometastases, omitting completion axillary lymph node dissection (CALND) is standard. High nodal burden (≥4 axillary nodal metastases) is an indication for intensified treatment in luminal breast cancer; hence, abstaining from CALND may result in undertreatment.

Objective

To develop a prediction model for high nodal burden in luminal ERBB2-negative breast cancer (all histologic types and lobular breast cancer separately) without CALND.

Design, Setting, and Participants

The prospective Sentinel Node Biopsy in Breast Cancer: Omission of Axillary Clearance After Macrometastases (SENOMAC) trial randomized patients 1:1 to CALND or its omission from January 2015 to December 2021 among adult patients with cN0 T1-T3 breast cancer and 1 or 2 SLN macrometastases across 5 European countries. The cohort was randomly split into training (80%) and test (20%) sets, with equal proportions of high nodal burden. Prediction models were developed by multivariable logistic regression in the complete luminal ERBB2-negative cohort and a lobular breast cancer subgroup. Nomograms were constructed. The present diagnostic/prognostic study presents the results of a prespecified secondary analysis of the SENOMAC trial. Herein, only patients with luminal ERBB2-negative tumors assigned to CALND were selected. Data analysis for this article took place from June 2023 to April 2024.

Exposure

Predictors of high nodal burden.

Main Outcomes and Measures

High nodal burden was defined as ≥4 axillary nodal metastases. The luminal prediction model was evaluated regarding discrimination and calibration.

Results

Of 1010 patients (median [range] age, 61 [34-90] years; 1006 [99.6%] female and 4 [0.4%] male), 138 (13.7%) had a high nodal burden and 212 (21.0%) had lobular breast cancer. The model in the training set (n = 804) included number of SLN macrometastases, presence of SLN micrometastases, SLN ratio, presence of SLN extracapsular extension, and tumor size (not included in lobular subgroup). Upon validation in the test set (n = 201), the area under the receiver operating characteristic curve (AUC) was 0.74 (95% CI, 0.62-0.85) and the calibration was satisfactory. At a sensitivity threshold of ≥80%, all but 5 low-risk patients were correctly classified corresponding to a negative predictive value of 94%. The prediction model for the lobular subgroup reached an AUC of 0.74 (95% CI, 0.66-0.83).

Conclusions and Relevance

The predictive models and nomograms may facilitate systemic treatment decisions without exposing patients to the risk of arm morbidity due to CALND. External validation is needed.

Trial Registration

ClinicalTrials.gov Identifier: NCT02240472.

"Lobular lesions of the breast: From the classic to the variants"

The aim of this review is to provide the surgical pathologist an overview of lobular lesions, from in situ to invasive carcinoma and the variants, by discussing the epidemiology, clinical characteristics, morphology, immunohistochemistry, known molecular data as well as the treatment recommendations. The recognition of histologic variants of both in situ and invasive lobular carcinoma has expanded the differential diagnosis. Awareness of these different entities is important as treatment recommendations continue to evolve.

E-Cadherin Mutational Landscape and Outcomes in Breast Invasive Lobular Carcinoma

Invasive lobular carcinomas (ILC) are characterized by the loss of E-cadherin expression and CDH1 gene inactivation. Diagnostic reproducibility for this tumor type is currently suboptimal and could be improved by a better understanding of its histomolecular and clinical heterogeneity. We have analyzed the relationship between the presence, type, or position of CDH1 mutations, E-cadherin expression, and clinicopathological features (including outcome) in a retrospective series of 251 primary ILC with a long follow-up (median: 9.5 years). The mutational status of E-cadherin gene (CDH1) was determined by RNA sequencing from frozen tumor samples. E-cadherin immunohistochemistry (IHC) was performed with antibodies directed against the intracellular domain (clone 4A2C7) and the extracellular domain (clone NCH38). IHC expression of p120 and β-catenin was also assessed in E-cadherin diffusely positive cases. Three major patterns of E-cadherin membrane expression were identified by IHC, with good agreement between the 2 clones (overall concordance: 83.8%, Kappa 0.67): null/focal expression (≤10%) (72.8% of cases for 4A2C7 and 83.8% for NCH38), heterogeneous expression (11%-89%) (19.2% of cases for 4A2C7 and 6.9% for NCH38), and diffuse expression (≥90%) (8% of cases for 4A2C7 and 9.3% for NCH38). E-cadherin membranous expression, when present, was abnormal (incomplete labeling and/or reduced intensity). ILC with diffuse E-cadherin expression showed abnormal β-catenin or p120-catenin staining in 21% of cases. Interestingly, these cases with diffusely expressed E-cadherin had a CDH1 mutation rate as high as the E-cadherin null/focal cases (∼70%) but were enriched in nontruncating mutations. Regarding CDH1 mutation location, intracytoplasmic domain mutations correlated with a divergent E-cadherin IHC phenotype between the 2 antibodies (4A2C7 ≤ 10%/NCH38 ≥ 10%). Clinico-pathological correlation analyses found that stromal amount (inversely correlated with tumor cellularity) and tumor-infiltrating lymphocytes were less abundant in ILC with E-cadherin null/focal cases. In addition, CDH1 truncating mutations were associated with radiohistologic size discordance and were identified in multivariate survival analysis as an independent poor prognosis factor in terms of metastasis risk and breast cancer-related mortality. Overall, our study highlights the importance of the precise mutational status of CDH1 in the clinical, radiological, histologic, and phenotypic expression of lobular carcinomas. These findings should be taken into account in future attempts to improve diagnostic criteria or methods for ILC, as well as for clinicobiological studies dedicated to this tumor type.

Invasive lobular carcinoma of the breast: we diagnose it, but do we know what it is?

Invasive lobular carcinoma of the breast is the most common special type breast cancer. It has been defined using morphological features, has a characteristic immunophenotype associated with the loss of E-cadherin mediated intercellular adhesion, and the background of this immunohistochemistry and morphology is generally a biallelic genetic alteration of the CDH-1 gene coding E-cadherin. However, the morphology may often deviate from the classical, and immunohistochemistry may also deviate from the typical, and then the diagnosis of invasive lobular carcinoma becomes less straight forward. Eventually, the definitions of this histological type, although similar, are not identical and this may also give ground to occasional different interpretations. This review summarizes different approaches to invasive lobular carcinomas and the deviations from what is considered normal.

Insights into E-Cadherin Impairment in CDH1-Unaltered Invasive Lobular Carcinoma: A Comprehensive Bioinformatic Study

Invasive lobular carcinoma exhibits unique morphological features frequently associated with alterations in CDH1. Although some studies have identified abnormalities in adhesion factors other than E-cadherin, the molecular mechanisms underlying E-cadherin abnormalities in CDH1-unaltered invasive lobular carcinoma remain poorly understood. In this study, we investigated the molecular underpinnings of E-cadherin dysregulation in invasive lobular carcinoma in the absence of CDH1 gene alterations, using comprehensive bioinformatic analyses. We conducted a comparative study of CDH1-mutated and non-mutated invasive lobular carcinoma and evaluated the differences in mRNA levels, reverse-phase protein array, methylation, and miRNAs. We observed that invasive lobular carcinoma cases without CDH1 alterations exhibited a significantly higher incidence of the Claudin-low subtype (p < 0.01). The results of the reverse-phase protein array indicate no significant difference in E-cadherin expression between CDH1-mutated and non-mutated cases. Therefore, abnormalities in E-cadherin production also exist in CDH1 non-mutated invasive lobular carcinoma. Considering that there are no differences in mRNA levels and methylation status, post-translational modifications are the most plausible explanation for the same. Hence, future studies should focus on elucidating the mechanism underlying E-cadherin inactivation via post-translational modifications in CDH1 non-mutated invasive lobular carcinoma.

Integration of Pathological Criteria and Immunohistochemical Evaluation for Invasive Lobular Carcinoma Diagnosis: Recommendations From the European Lobular Breast Cancer Consortium

Invasive lobular carcinoma (ILC) is the second most frequent type of breast cancer (BC) and its peculiar morphology is mainly driven by inactivation of CDH1, the gene coding for E-cadherin cell adhesion protein. ILC-specific therapeutic and disease-monitoring approaches are gaining momentum in the clinic, increasing the importance of accurate ILC diagnosis. Several essential and desirable morphologic diagnostic criteria are currently defined by the World Health Organization, the routine use of immunohistochemistry (IHC) for E-cadherin is not recommended. Disagreement in the diagnosis of ILC has been repeatedly reported, but interpathologist agreement increases with the use of E-cadherin IHC. In this study, we aimed to harmonize the pathological diagnosis of ILC by comparing 5 commonly used E-cadherin antibody clones (NCH-38, EP700Y, Clone 36, NCL-L-E-cad [Clone 36B5], and ECH-6). We determined their biochemical specificity for the E-cadherin protein and IHC staining performance according to type and location of mutation on the CDH1 gene. Western blot analysis on mouse cell lines with conditional E-cadherin expression revealed a reduced specificity of EP700Y and NCL-L-E-cad for E-cadherin, with cross-reactivity of Clone 36 to P-cadherin. The use of IHC improved interpathologist agreement for ILC, lobular carcinoma in situ, and atypical lobular hyperplasia. The E-cadherin IHC staining pattern was associated with variant allele frequency and likelihood of nonsense-mediated RNA decay but not with the type or position of CDH1 mutations. Based on these results, we recommend the indication for E-cadherin staining, choice of antibodies, and their interpretation to standardize ILC diagnosis in current pathology practice.

The Alveolar Variant of Lobular Carcinoma and Its Mimickers: A Case Series

Invasive lobular carcinoma (ILC) is the most common special type of invasive breast cancer (IBC), accounting for 5-15% of IBCs. The distinct histomorphology of ILC reflects a special tumor biology, the hallmark of which is the lack of E-cadherin expression. However, the occasional presence of E-cadherin expression and the presence of IBC of no special type (IBC, NST)-like morphologies in ILC and vice versa make the diagnosis challenging.  We present two cases of the alveolar variant of ILC, a diagnostically challenging entity. The first case is an 81-year-old female with two discrete right breast masses at 1 o'clock and 9 o'clock positions.  The second case is a 61-year-old female with two discrete left breast masses located at 11 o'clock and 12 o'clock positions. Core needle biopsies and subsequent mastectomy were performed in both cases. On histology, three tumor foci were identified in the first case. The 1 o'clock focus showed IBC, NST, grade 3/3, ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). The 9 o'clock focus revealed ILC, classic and alveolar variants, grade 2/3, while a nearby third incidental focus was ILC, alveolar variant, both supported by lack of E-cadherin and β-catenin immunostaining.  The second case showed ILC, alveolar variant, grade 1 with LCIS component in the 11 o'clock lesion on both biopsy and mastectomy specimens. The lesion at the 12 o'clock position was diagnosed as IBC, NST, grade 2 with high-grade DCIS and LCIS components.  It is challenging to distinguish the alveolar variant of ILC from IBC, NST, and in situ lesions because of the overlapping morphology and occasional E-cadherin expression. Altered adherence of lobular cells may also be due to loss of α-, β-, and γ-catenins, and cytoplasmic re-localization of p120-catenin. Therefore, in ILC, the lack of β-catenin can be used as an adjunct along with E-cadherin. Myoepithelial markers such as p63 and smooth muscle myosin heavy chain (SMMHC) can be used to distinguish the alveolar variant of ILC from LCIS.

Updates in the Use of Immunohistochemical Stains in Breast and Gynecologic Pathology

CONTEXT.—

The use of immunohistochemical stains in breast and gynecologic pathology has become increasingly complex, with various diagnostic, prognostic, and predictive applications.

OBJECTIVE.—

To provide an update and review of immunohistochemical stains used in the practice of breast and gynecologic pathology. Established and new entities are reviewed, with descriptions of histomorphology and immunohistochemical staining patterns and discussion of interpretive pitfalls.

DATA SOURCES.—

Data were obtained from review of the English-language literature and firsthand experience of the authors in breast and gynecologic pathology.

CONCLUSIONS.—

Many entities in breast and gynecologic pathology benefit from evaluation with various immunohistochemical stains. These studies not only aid in the diagnosis and staging of tumors but also can provide prognostic and predictive information. Updated guidelines for recommended ancillary studies such as mismatch repair, p53, and human epidermal growth factor receptor 2 (HER2) studies in endometrium, as well as estrogen and progesterone receptors and HER2 in breast, are discussed. Finally, the use and interpretation of established and novel immunohistochemical stains are discussed in various breast and gynecologic malignancies.

Implementing an On-Slide Molecular Classification of Gastric Cancer: A Tissue Microarray Study

Background and Objectives: Gastric cancer (GC) is one of the most commonly diagnosed cancers and the fourth cause of cancer death worldwide. Personalised treatment improves GC outcomes. A molecular classification is needed to choose the appropriate therapy. A classification that uses on-slide biomarkers and formalin-fixed and paraffin-embedded (FFPE) tissue is preferable to comprehensive genomic analysis. In 2016, Setia and colleagues proposed an on-slide classification; however, this is not in widespread use. We propose a modification of this classification that has six subgroups: GC associated with Epstein-Barr virus (GC EBV+), GC with mismatch-repair deficiency (GC dMMR), GC with epithelial-mesenchymal transformation (GC EMT), GC with chromosomal instability (GC CIN), CG that is genomically stable (GC GS) and GC not otherwise specified (GC NOS). This classification also has a provision for biomarkers for current or emerging targeted therapies (Her2, PD-L1 and Claudin18.2). Here, we assess the implementation and feasibility of this inclusive working classification. Materials and Methods: We constructed a tissue microarray library from a cohort of 79 resection cases from FFPE tissue archives. We used a restricted panel of on-slide markers (EBER, MMR, E-cadherin, beta-catenin and p53), defined their interpretation algorithms and assigned each case to a specific molecular subtype. Results: GC EBV(+) cases were 6%, GC dMMR cases were 20%, GC EMT cases were 14%, GC CIN cases were 23%, GC GS cases were 29%, and GC NOS cases were 8%. Conclusions: This working classification uses markers that are widely available in histopathology and are easy to interpret. A diagnostic subgroup is obtained for 92% of the cases. The proportion of cases in each subgroup is in keeping with other published series. Widescale implementation appears feasible. A study using endoscopic biopsies is warranted.

Evaluation of the routine use of E-cadherin immunohistochemistry in the typing of breast carcinomas: results of a randomized diagnostic study

AIMS

Invasive lobular carcinoma (ILC) has distinct morphology and association with loss of E-cadherin function. It has special clinical and imaging features, and its proper recognition is important. Following a recent proposal, we tested the value of the routine use of E-cadherin immunohistochemistry (IHC) in recognizing ILC.

METHODS AND RESULTS

Five pathologists with experience in breast pathology from four Hungarian institutions histotyped 1001 breast cancers from diagnostic core biopsies or excision specimens randomly assigned to haematoxylin and eosin (HE) diagnosis first, followed by E-cadherin IHC; or to immediate HE and E-cadherin-based diagnosis. Of 524 cases with HE diagnosis, 73(14%) were deemed uncertain. E-cadherin made the initial histological type change in 14/524 cases (2.7%), including three with confident HE-based type allocation. Use of E-cadherin immunostaining was considered useful in 88/477 cases (18%) with immediate dual assessment, and typing uncertainty went down to 5% (25/477 cases), but was not zero. Collective assessment of 171 uncertain, difficult, nonclassical cases resulted in consensus diagnosis in most cases, but 15 cases were still doubtful as concerns their proper histological type. CDH1 gene sequencing was attempted and successful in 13; pathogenic genetic alterations were identified in seven cases.

CONCLUSIONS

The routine use of E-cadherin IHC decreases the uncertainty in typing and improves the typing accuracy at the cost of potentially redundant additional immunostains. Furthermore, this procedure does not exclude uncertainty due to E-cadherin-positive ILCs, which are occasionally difficult to confidently label as ILC, especially when the growth pattern is not classic.

Immunohistochemistry in the Diagnosis and Classification of Breast Tumors

CONTEXT.—

In the clinical practice of breast pathology, immunohistochemistry (IHC) of different markers is widely used for the diagnosis and classification of breast lesions.

OBJECTIVE.—

To provide an overview of currently used and recently identified IHC stains that have been implemented in the field of diagnostic breast pathology.

DATA SOURCES.—

Data were obtained from literature review and clinical experience of the authors as breast pathologists.

CONCLUSIONS.—

In the current review, we summarize the common uses of IHC stains for diagnosing different types of breast lesions, especially invasive and noninvasive breast lesions, and benign and malignant spindle cell lesions. In addition, the cutting-edge knowledge of diagnostic carcinoma markers will lead us to further understand the different types of breast carcinoma and differentiate breast carcinomas from other carcinomas of similar morphology. Knowing the strengths and limitations of these markers is essential to the clinical practice of breast pathology.

Diagnostic Pitfalls in Breast Cancer Pathology With an Emphasis on Core Needle Biopsy Specimens

CONTEXT.—

Breast pathology has many mimics and diagnostic pitfalls. Evaluation of malignant breast lesions, particularly in the biopsy setting, can be especially challenging, with diagnostic errors having significant management implications.

OBJECTIVE.—

To discuss the pitfalls encountered when evaluating ductal carcinoma in situ and invasive breast carcinomas, providing histologic clues and guidance for appropriate use and interpretation of immunohistochemistry to aid in the correct diagnosis.

DATA SOURCES.—

Data were obtained from review of pertinent literature of ductal carcinoma in situ and invasive breast carcinomas and from the experience of the authors as practicing breast pathologists.

CONCLUSIONS.—

Awareness of the pitfalls in diagnosing breast cancers is important when creating a differential diagnosis for each breast lesion evaluated. This review will cover some of these scenarios to aid in the diagnostic process.

Clinicopathologic and genomic features of lobular like invasive mammary carcinoma: is it a distinct entity?

This study describes "lobular-like invasive mammary carcinomas" (LLIMCas), a group of low- to intermediate-grade invasive mammary carcinomas with discohesive, diffusely infiltrative cells showing retained circumferential membranous immunoreactivity for both E-cadherin and p120. We analyzed the clinical-pathologic features of 166 LLIMCas compared to 104 classical invasive lobular carcinomas (ILCs) and 100 grade 1 and 2 invasive ductal carcinomas (IDCs). Tumor size and pT stage of LLIMCas were intermediate between IDCs and ILCs, and yet often underestimated on imaging and showed frequent positive margins on the first resection. Despite histomorphologic similarities to classical ILC, the discohesion in LLIMCa was independent of E-cadherin/p120 immunophenotypic alteration. An exploratory, hypothesis-generating analysis of the genomic features of 14 randomly selected LLIMCas and classical ILCs (7 from each category) was performed utilizing an FDA-authorized targeted capture sequencing assay (MSK-IMPACT). None of the seven LLIMCas harbored CDH1 loss-of-function mutations, and none of the CDH1 alterations detected in two of the LLIMCas was pathogenic. In contrast, all seven ILCs harbored CDH1 loss-of-function mutations coupled with the loss of heterozygosity of the CDH1 wild-type allele. Four of the six evaluable LLIMCas were positive for CDH1 promoter methylation, which may partially explain the single-cell infiltrative morphology seen in LLIMCa. Further studies are warranted to better define the molecular basis of the discohesive cellular morphology in LLIMCa. Until more data becomes available, identifying LLIMCas and distinguishing them from typical IDCs and ILCs would be justified. In patients with LLIMCas, preoperative MRI should be entertained to guide surgical management.

Duplex Phenotype Detection and Targeting of Breast Cancer Cells Using Nanotube Nanoprobes and Raman Imaging

We designed, synthesized, and characterized a Raman nanoprobe made of dye-sensitized single-walled carbon nanotubes (SWCNTs) that can selectively target biomarkers of breast cancer cells. The nanoprobe is composed of Raman-active dyes encapsulated inside a SWCNT, whose surface is covalently grafted with poly(ethylene glycol) (PEG) at a density of ∼0.7% per carbon. Using α-sexithiophene- and β-carotene-derived nanoprobes covalently bound to an antibody, either anti-E-cadherin (E-cad) or anti-keratin-19 (KRT19), we prepared two distinct nanoprobes that specifically recognize biomarkers on breast cancer cells. Immunogold experiments and transmission electron microscopy (TEM) images are first used to guide the synthesis protocol for higher PEG-antibody attachment and biomolecule loading capacity. The duplex of nanoprobes was then applied to target E-cad and KRT19 biomarkers in T47D and MDA-MB-231 breast cancer cell lines. Hyperspectral imaging of specific Raman bands allows for simultaneous detection of this nanoprobe duplex on target cells without the need for additional filters or subsequent incubation steps. Our results confirm the high reproducibility of the nanoprobe design for duplex detection and highlight the potential of Raman imaging for advanced biomedical applications in oncology.

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.

Pitfalls in breast pathology

Accurate pathological diagnosis is the cornerstone of optimal clinical management for patients with breast disease. As non-operative diagnosis has now become the standard of care, histopathologists encounter the daily challenge of making definitive diagnoses on limited breast core needle biopsy (CNB) material. CNB samples are carefully evaluated using microscopic examination of haematoxylin and eosin (H&E)-stained slides and supportive immunohistochemistry (IHC), providing the necessary information to inform the next steps in the patient care pathway. Some entities may be difficult to distinguish on small tissue samples, and if there is uncertainty a diagnostic excision biopsy should be recommended. This review discusses (1) benign breast lesions that may mimic malignancy, (2) malignant conditions that may be misinterpreted as benign, (3) malignant conditions that may be incorrectly diagnosed as primary breast carcinoma, and (4) some IHC pitfalls. The aim of the review is to raise awareness of potential pitfalls in the interpretation of breast lesions that may lead to underdiagnosis, overdiagnosis, or incorrect classification of malignancy with potential adverse outcomes for individual patients.

The morphologic spectrum of lobular carcinoma in situ (LCIS) observations on clinical significance, management implications and diagnostic pitfalls of classic, florid and pleomorphic LCIS

Lobular carcinoma in situ (LCIS) is a non-invasive proliferation of atypical dyscohesive epithelial cells characterized by loss or functional alteration of E-cadherin-mediated cell adhesion. The morphologic spectrum of LCIS encompasses classic (C-LCIS), florid (F-LCIS) and pleomorphic LCIS (P-LCIS), as recently defined by the World Health Organization (WHO) Expert Consensus Group. Atypical lobular hyperplasia (ALH) is also part of this spectrum.This article highlights the morphologic and immunohistochemical features of the three forms of LCIS and summarizes their management implications and prognosis, with emphasis on F-LCIS and P-LCIS.

Invasive lobular carcinoma with extracellular mucin (ILCEM): clinicopathologic and molecular characterization of a rare entity

Invasive lobular carcinoma with extracellular mucin (ILCEM) is a rare histologic subtype of breast cancer. Little is known about the pathologic or genomic signatures that distinguish ILCEM from classic invasive lobular carcinoma (ILC) or mucinous carcinoma. We studied 17 breast cancers with lobular morphology and extracellular mucin. Thirteen tumors with sufficient tissue for DNA extraction were analyzed by a next generation sequencing (NGS) assay that interrogates 447 genes for mutations and copy number variations (CNVs). Median patient age was 66 yrs (range: 31-77 yrs). Sixteen patients presented with masses, 7 of which were >2 cm. Seven patients had lymph node metastases. The cases of ILCEM were moderately (n = 13) or poorly differentiated (n = 4), frequently exhibiting variant morphology that has not been previously described or emphasized, including grade 3 nuclei (n = 11), diffuse signet ring cells (n = 10), solid growth (n = 4), tumor necrosis (n = 3) or apocrine features (n = 2). All tumors showed absent or reduced membranous E-cadherin expression. Concurrent lobular carcinoma in situ (LCIS) was seen in 11/17 cases, 1 of which was a striking example of signet ring cell LCIS with extracellular mucin. Receptor profiles were ER+/HER2- (n = 15) and ER+/HER2+ (n = 2). With a median follow-up of 83.5 months (range: 3-171 months) in 12 patients with available information, 8 patients had recurrences resulting in 4 cancer-related deaths. The most common CNVs were 16q loss (n = 11) and 1q gain (n = 9). CDH1 gene-level alterations were detected in all but one case, including frameshift (n = 7), nonsense (n = 2), and donor splice site (n = 1) mutations and indels (n = 2). Recurrent mutations were also seen in PIK3CA (n = 3), POLQ (n = 3), TP53 (n = 3), ERBB3 (n = 3), ERBB2 (n = 2), and RUNX1 (n = 2). Genes with recurrent amplifications included GATA3 (n = 4), FOXA1 (n = 3), CCND1 (n = 2). Our data highlights ILCEM as a distinct variant of ILC that often presents with higher-grade and variant morphologic features and is associated with an aggressive clinical course. NGS data support an overall lobular-type molecular profile and reveal potentially targetable alterations in a subset of cases with recurrence.

Aquaporin-5 in breast cancer

The water channel aquaporin‐5 (AQP5) is essential in transepithelial water transport in secretory glands. AQP5 is ectopically overexpressed in breast cancer, where expression is associated with lymph node metastasis and poor prognosis. Besides the role in water transport, AQP5 has been found to play a role in cancer metastasis, migration, and proliferation. AQP5 has also been shown to be involved in the dysregulation of epithelial cell–cell adhesion; frequently observed in cancers. Insight into the underlying molecular mechanisms of how AQP5 contributes to cancer development and progression is essential for potentially implementing AQP5 as a prognostic biomarker and to develop targeted intervention strategies for the treatment of breast cancer patients.

Expression of N-Terminal-Deficient E-Cadherin Protein in Invasive Lobular Carcinoma of the Breast

Invasive lobular carcinoma (ILC) of the breast is characterized by the discohesive growth of tumor cells, which is mainly associated with the complete loss of E-cadherin (E-cad) expression. However, some aberrant expression patterns of E-cad protein that are inconsistent with their morphologies have been reported in ILC. We report herein ILC cases expressing a new type of abnormal E-cad protein that lacks the N-terminal domain, but conserves the C-terminal domain on the cell membrane. Immunohistochemical staining of 299 ILC cases using specific antibodies against the N-terminal or C-terminal region of E-cad revealed that 227 (76%) cases showed loss of the membranous expression of both terminuses (N-/C-) and 72 (24%) cases showed expression of only the C-terminus (N-/C+). In all cases, the expression of p120-catenin and β-catenin coincided with the expression of the C-terminus of E-cad. Clinicopathologic analysis revealed that N-/C+ expression in ILC cells was significantly associated with the histologic subtype (especially mixed-type ILC with another histologic type) and immunohistochemical molecular subtype (especially the triple-negative subtype), but not with prognostic factors (pT or pN). In addition, 12 of 15 cases (80%) with aberrant cytoplasmic localization of the N-terminal of E-cad showed diffuse membranous expression of the C-terminal domain. Additional immunohistochemistry using an antibody recognizing the extracellular juxtamembrane region showed that 28 (39%) of the N-/C+ cases had lost membranous expression, suggesting diversity in the deletion pattern of the N-terminal region. Our findings provide a novel mechanism for the loss of E-cad function because of N-terminal-deficient E-cad protein in ILC.

Results of a worldwide survey on the currently used histopathological diagnostic criteria for invasive lobular breast cancer

Invasive lobular carcinoma (ILC) represents the second most common subtype of breast cancer (BC), accounting for up to 15% of all invasive BC. Loss of cell adhesion due to functional inactivation of E-cadherin is the hallmark of ILC. Although the current world health organization (WHO) classification for diagnosing ILC requires the recognition of the dispersed or linear non-cohesive growth pattern, it is not mandatory to demonstrate E-cadherin loss by immunohistochemistry (IHC). Recent results of central pathology review of two large randomized clinical trials have demonstrated relative overdiagnosis of ILC, as only ~60% of the locally diagnosed ILCs were confirmed by central pathology. To understand the possible underlying reasons of this discrepancy, we undertook a worldwide survey on the current practice of diagnosing BC as ILC. A survey was drafted by a panel of pathologists and researchers from the European lobular breast cancer consortium (ELBCC) using the online tool SurveyMonkey®. Various parameters such as indications for IHC staining, IHC clones, and IHC staining procedures were questioned. Finally, systematic reporting of non-classical ILC variants were also interrogated. This survey was sent out to pathologists worldwide and circulated from December 14, 2020 until July, 1 2021. The results demonstrate that approximately half of the institutions use E-cadherin expression loss by IHC as an ancillary test to diagnose ILC and that there is a great variability in immunostaining protocols. This might cause different staining results and discordant interpretations. As ILC-specific therapeutic and diagnostic avenues are currently explored in the context of clinical trials, it is of importance to improve standardization of histopathologic diagnosis of ILC diagnosis.

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.

Lobular Breast Cancer: Histomorphology and Different Concepts of a Special Spectrum of Tumors

Simple Summary

Invasive lobular breast cancer (ILC) is a special type of breast cancer (BC) that was first described in 1941. The diagnosis of ILC is made by microscopy of tumor specimens, which reveals a distinct morphology. This review recapitulates the developments in the microscopic assessment of ILC from 1941 until today. We discuss different concepts of ILC, provide an overview on ILC variants, and highlight advances which have contributed to a better understanding of ILC as a special histologic spectrum of tumors.

Abstract

Invasive lobular breast cancer (ILC) is the most common special histological type of breast cancer (BC). This review recapitulates developments in the histomorphologic assessment of ILC from its beginnings with the seminal work of Foote and Stewart, which was published in 1941, until today. We discuss different concepts of ILC and their implications. These concepts include (i) BC arising from mammary lobules, (ii) BC growing in dissociated cells and single files, and (iii) BC defined as a morpho-molecular spectrum of tumors with distinct histological and molecular characteristics related to impaired cell adhesion. This review also provides a comprehensive overview of ILC variants, their histomorphology, and differential diagnosis. Furthermore, this review highlights recent advances which have contributed to a better understanding of the histomorphology of ILC, such as the role of the basal lamina component laminin, the molecular specificities of triple-negative ILC, and E-cadherin to P-cadherin expression switching as the molecular determinant of tubular elements in CDH1-deficient ILC. Last but not least, we provide a detailed account of the tumor microenvironment in ILC, including tumor infiltrating lymphocyte (TIL) levels, which are comparatively low in ILC compared to other BCs, but correlate with clinical outcome. The distinct histomorphology of ILC clearly reflects a special tumor biology. In the clinic, special treatment strategies have been established for triple-negative, HER2-positive, and ER-positive BC. Treatment specialization for patients diagnosed with ILC is just in its beginnings. Accordingly, ILC deserves greater attention as a special tumor entity in BC diagnostics, patient care, and cancer research.

Triple-negative breast lobular carcinoma: a luminal androgen receptor carcinoma with specific ESRRA mutations

Primary triple-negative invasive lobular breast carcinomas (TN-ILCs), which do not express hormone receptors and HER2 at diagnosis, are rare and poorly known. In this study, we analyzed the largest TN-ILC series ever reported in the literature, in comparison to phenotypically similar breast tumor subtypes: triple-negative invasive ductal carcinoma (TN-IDC) and hormone receptor-positive invasive lobular carcinoma (HR + ILC). All primary TN-ILCs registered in our database between 2000 and 2018 (n = 38) were compared to tumors from control groups, matched by stage and Elston/Ellis grade, with regard to clinical, pathologic, and immunohistochemical characteristics. A comparative molecular analysis (whole-exome and RNA sequencing using next-generation technology) was also performed. We found that TN-ILC patients were older than those with HR + ILC (P = 0.002) or TN-IDC (P < 0.001). Morphologically, TN-ILCs had aggressive phenotypes, with more pleomorphism (P = 0.003) and higher nuclear grades than HR + ILCs (P = 0.009). Immunohistochemistry showed that TN-ILCs less frequently expressed basal markers (CK5/6, EGFR and SOX10) than TN-IDCs (P < 0.001), while androgen receptor (AR) positivity was more prevalent (P < 0.001). Survival curves analysis did not show differences between TN-ILC and TN-IDC patients, while overall and distant metastasis-free survival were significantly worse compared to those with HR + ILCs (P = 0.047 and P = 0.039, respectively). At a molecular level, we found that TN-ILCs had particular transcriptomic profiles, characterized by increased AR signaling, and associated with frequent alterations in the PI3K network and ERBB2. Interestingly, whole-exome analysis also identified three specific recurrent ESRRA hotspot mutations in these tumors, which have never been described in breast cancer to date and which were absent in the other two tumor subtypes. Our findings highlight that TN-ILC is a unique aggressive breast cancer associated with elderly age, which belong to the luminal androgen receptor subtype as determined by immunohistochemistry and transcriptomic profiling. Moreover, it harbors specific molecular alterations (PI3K, ERBB2 and ESRRA) which may pave the way for new targeted therapeutic strategies.

Mixed ductal-lobular carcinoma: an analysis of CDH1 DNA copy number variation and mutation

BACKGROUND

Mixed ductal-lobular carcinoma (MDL) of the breast is poorly understood. Dysfunction of E-cadherin, a cell adhesion protein encoded by the CDH1 gene located on 16q22.1, causes loss of cell adhesion and cellular polarity in lobular carcinoma (LC). This study focuses the aberrations of CDH1 in LC, ductal carcinoma (DC), and MDL to investigate the pathogenesis of MDL.

METHODS

The CDH1 DNA value (ratio of CDH1 copy number to the reference gene, RNase P) was calculated by digital polymerase chain reaction analysis of a total of 113 breast carcinoma cases (51 LCs, 54 DCs, and 8 MDLs). CDH1 gene mutation assay was performed for 20/51 LCs, 8/54 DCs, and 8 MDLs cases.

RESULTS

The CDH1 DNA values were lower in LCs (average: 0.664) than in DCs (average: 1.296) (p < 0.000). In MDL, The CDH1 DNA values were significantly lower in LC areas (average: 0.58), compared to that of DC areas (average: 1.08) (p = 0.004), and there is no significant difference between the intermingled areas (average: 1.05) and DC areas (p = 0.775). Moreover, CDH1 mutations occurred more frequently in MDLs than in pure LCs and DCs. In one MDL case, the identical CDH1 mutation was found in LC and DC areas.

CONCLUSION

Our study presented that MDL had more frequent CDH1 mutations. There were two possible processes for cancer cells in LC areas: one process was via DC areas with a common ancestor, and another was an independent process from DC areas.

Histological type and typing of breast carcinomas and the WHO classification changes over time

The World Health Organization’s new classification of breast tumors has just been published. This review aims to examine the morphological categorization of breast carcinomas which is still principally based on histological features and follows the traditions of histological typing. It gives a subjective and critical view on the WHO classifications and their changes over time, and describes the changes related to some of the most common or challenging breast carcinomas: in situ carcinomas, invasive breast carcinomas of no special type, lobular, cribriform, tubular, mucinous, papillary, metaplastic carcinomas and carcinomas with medullary pattern and those with apocrine differentiation are discussed in more details. Although the 5^th edition of the classification is not perfect, it has advantages which are mentioned along with problematic issues of classifications.

Hereditary diffuse gastric cancer: updated clinical practice guidelines

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer syndrome that is characterised by a high prevalence of diffuse gastric cancer and lobular breast cancer. It is largely caused by inactivating germline mutations in the tumour suppressor gene CDH1, although pathogenic variants in CTNNA1 occur in a minority of families with HDGC. In this Policy Review, we present updated clinical practice guidelines for HDGC from the International Gastric Cancer Linkage Consortium (IGCLC), which recognise the emerging evidence of variability in gastric cancer risk between families with HDGC, the growing capability of endoscopic and histological surveillance in HDGC, and increased experience of managing long-term sequelae of total gastrectomy in young patients. To redress the balance between the accessibility, cost, and acceptance of genetic testing and the increased identification of pathogenic variant carriers, the HDGC genetic testing criteria have been relaxed, mainly through less restrictive age limits. Prophylactic total gastrectomy remains the recommended option for gastric cancer risk management in pathogenic CDH1 variant carriers. However, there is increasing confidence from the IGCLC that endoscopic surveillance in expert centres can be safely offered to patients who wish to postpone surgery, or to those whose risk of developing gastric cancer is not well defined.

Genomic profiling of pleomorphic and florid lobular carcinoma in situ reveals highly recurrent ERBB2 and ERRB3 alterations

Pleomorphic LCIS (P-LCIS) and florid LCIS (F-LCIS) are morphologic variants distinguished from classic LCIS by marked nuclear pleomorphism and/or an expansile growth pattern with or without necrosis. Given the rarity of these LCIS variants, little data exist regarding their molecular pathogenesis, natural history, and optimal management. The purpose of this study was to genomically profile LCIS variants to gain further insight into their biology. Nineteen cases of pure LCIS variants (17 P-LCIS, 2 F-LCIS) diagnosed on core needle biopsy at our institution from 2006 to 2017 were included, five of which were upgraded to invasive cancer at excision. Macrodissected lesions were analyzed by a hybrid-capture next generation sequencing assay that surveyed exonic sequences of 447 genes for mutations and copy number variations (CNVs) and 191 regions across 60 genes for structural rearrangements. LCIS variants were all confirmed as E-cadherin negative by immunohistochemistry. Receptor profiles among the 17 P-LCIS cases included HR+/HER2- (nine cases), HR+/HER2+ (three cases), HR-/HER2+ (two cases), and HR-/HER2- (three cases). The two F-LCIS cases were HR+/HER2- and HR+/HER2+. All LCIS variants had genetic alterations consistent with a lobular phenotype including 1q gain (16 cases), 16q loss (18 cases), and CDH1 mutations (18 cases). Highly recurrent ERBB2 alterations were noted including mutations (13 cases) and amplifications (six cases). Other significant alterations included mutations in PIK3CA (six cases), RUNX1 (four cases), ERBB3 (four cases), and CBFB (three cases), as well as amplification of CCND1 (five cases). A TP53 mutation was identified in one case of HR-/HER2+ P-LCIS with signet ring cell features that lacked 1q gain and 16q loss. P-LCIS and F-LCIS contain genetic alterations characteristic of lobular neoplasia; however, these LCIS variants are distinguished from classical LCIS reported in the literature by their highly recurrent ERBB2 alterations.

E-cadherin immunohistochemical expression in invasive lobular carcinoma of the breast: correlation with morphology and CDH1 somatic alterations

E-cadherin (ECAD) immunohistochemical (IHC) expression is lost in ∼90% of invasive lobular carcinomas (ILCs) owing to genomic alterations of CDH1. We examined morphologic features and ECAD IHC expression in invasive breast carcinomas (BCs) with known CDH1 alterations. Between January 2014 and May 2018, 202 cases of BC with a CDH1 somatic alteration were identified. ECAD expression was lost in 77% (155/202) of cases and was retained in 23% (47/202) cases. Most (90%, 139/155) ECAD-negative cases were morphologically classified as ILC, while the remaining (10%, 16/155) were invasive mammary carcinoma with mixed ductal and lobular features (IMC). Of 47 cases with ECAD staining, 62% (29/47) were classified as ILC, 23% (11/47) were classified as IMC, and 15% (7/47) were classified as invasive ductal carcinoma (IDC). Of note, 51% (24/47) of ECAD-positive cases were initially diagnosed as IDC or IMC based on ECAD expression alone. For ECAD-negative BCs, 98% (152/155) of CDH1 alterations were truncating, and 2% (3/155) were variants of unknown significance (VUS). Truncating CDH1 alterations were identified in the majority of ECAD-positive BCs (72%, 34/47); however, VUS-type CDH1 alterations were more prevalent (28%, 13/47) in ECAD-positive BCs than in ECAD-negative BCs. Although 90% of ECAD-negative tumors were compatible with ILC in this study, 17% (29/168) of ILC cases were ECAD positive. In addition, CDH1 truncating alterations were seen in ECAD-positive ILC, supporting the notion of aberrant ECAD staining. Therefore, ECAD IHC expression must be interpreted in conjunction with morphology, and BC with classic histologic features of ILC should not be reclassified as IDC/IMC based solely on the status of ECAD IHC expression.

A review on methods for diagnosis of breast cancer cells and tissues

Breast cancer has seriously been threatening physical and mental health of women in the world, and its morbidity and mortality also show clearly upward trend in China over time. Through inquiry, we find that survival rate of patients with early‐stage breast cancer is significantly higher than those with middle‐ and late‐stage breast cancer, hence, it is essential to conduct research to quickly diagnose breast cancer. Until now, many methods for diagnosing breast cancer have been developed, mainly based on imaging and molecular biotechnology examination. These methods have great contributions in screening and confirmation of breast cancer. In this review article, we introduce and elaborate the advances of these methods, and then conclude some gold standard diagnostic methods for certain breast cancer patients. We lastly discuss how to choose the most suitable diagnostic methods for breast cancer patients. In general, this article not only summarizes application and development of these diagnostic methods, but also provides the guidance for researchers who work on diagnosis of breast cancer.

Non-invasive lobular neoplasia of the breast: Morphologic features, clinical presentation, and management dilemmas

The designation of noninvasive lobular neoplasia applies to atypical epithelial proliferations composed of noncohesive cells secondary to loss or functional alteration of E-cadherin-mediated cell adhesion. The morphologic spectrum of noninvasive lobular neoplasia encompasses atypical lobular hyperplasia (ALH) and classic lobular carcinoma in situ (classic LCIS) and two LCIS variants, namely florid LCIS (F-LCIS) and pleomorphic LCIS (P-LCIS), as defined in the World Health Organization (WHO) Classification of Tumors of the Breast 5th ed. Herein, we review the morphologic, immunohistochemical, and molecular features of noninvasive lobular neoplasia, with special emphasis on F-LCIS and P-LCIS. We also review imaging features, management at core needle biopsy, upgrade rates at surgical excision, and clinical management dilemmas.

BMP-2 Variants in Breast Epithelial to Mesenchymal Transition and Microcalcifications Origin

This study aims to investigate the possible different roles of the BMP-2 variants, cytoplasmic and nuclear variant, in both epithelial to mesenchymal transition and in microcalcifications origin in human breast cancers. To this end, the in situ expression of cytoplasmic and nuclear BMP-2 was associated with the expression of the main epithelial to mesenchymal transition biomarkers (e-cadherin and vimentin) and molecules involved in bone metabolisms (RUNX2, RANKL, SDF-1) by immunohistochemistry. In addition, the expression of cytoplasmic and nuclear BMP-2 was associated with the presence of microcalcifications. Our data showed a significant association among the number of cytoplasmic BMP-2-positive cells and the number of both vimentin (positive association) and e-cadherin (negative association) positive breast cells. Conversely, no associations were found concerning the nuclear BMP-2-positive breast cells. Surprisingly, the opposite result was obtained by analyzing the variants of BMP-2 and both the expression of RANKL and SDF-1 and the presence of microcalcifications. Specifically, the presence of microcalcifications was related to the expression of nuclear BMP-2 variant rather than the cytoplasmic one, as well as a strong association between the number of nuclear BMP-2 and the expression of the main breast osteoblast-like cells (BOLCs) biomarkers. To further corroborate these data, an in vitro experiment for demonstrating the co-expression of nBMP-2 and RANKL or vimentin or SDF-1 in breast cancer cells that acquire the capability to produce microcalcifications was developed. These investigations confirmed the association between the nBMP-2 expression and both RANKL and SDF-1. The data supports the idea that whilst cytoplasmic BMP-2 can be involved in epithelial to mesenchymal transition phenomenon, the nuclear variant is related to the essential mechanisms for the formation of breast microcalcifications. In conclusion, from these experimental and translational perspectives, the complexity of BMP-2 signaling will require a detailed understanding of the involvement of specific BMP-2 variants in breast cancers.

Genotype-phenotype associations in breast pathology: Achievements of the past quarter century

The first genotype-phenotype relationship in breast pathology developed in 1994 with the discovery of the CDH1 gene. This finding eventually provided biological insight into the characteristic morphology of invasive lobular carcinoma. Subsequent investigative efforts have uncovered additional molecular alterations largely responsible for the histology of several breast neoplasms including secretory carcinoma, adenoid cystic carcinoma, tall cell carcinoma with reversed polarity, fibroepithelial lesions, and most recently, adenomyoepithelioma. Evaluation of the genomic landscape of other special types of breast cancer with distinctive growth patterns, such as invasive mucinous carcinoma, have yet to uncover recurring cytogenetic and/or molecular alterations. Despite the lack of a hallmark alteration in mucinous carcinoma, it is important to note the relative decrease in PIK3CA mutations compared with invasive carcinoma of no special type. In this review, we describe the clinical and pathologic features of breast tumors with recognized genotype-phenotype correlations and summarize the molecular alterations of mucinous carcinoma.

American Registry of Pathology Expert Opinions: The Spectrum of Lobular Carcinoma in Situ: Diagnostic Features and Clinical Implications

This review reflects a collaboration between the American Registry of Pathology (the publisher of the Armed Forces Institute of Pathology Fascicles) and Annals of Diagnostic Pathology. It is part of a series of expert recommendations on topics encountered in daily practice. The authors, 4 pathologists with expertise in breast pathology and a breast surgeon with a clinical and research interest in lobular carcinoma in situ (LCIS), met by conference call in September 2019 to develop recommendations for evaluating and reporting LCIS. Herein, we summarize the diagnostic criteria of classic LCIS and LCIS subtypes according to the most recent WHO criteria, discuss how best to distinguish LCIS from ductal carcinoma in situ in problematic cases (including the uses and limitations of E-cadherin immunohistochemistry), and review outcome and management issues for patients with LCIS.

Pitfalls and controversies in pathology impacting breast cancer management

Introduction: Breast cancer is a heterogeneous disease, at morphological, molecular, and clinical levels and this has significant implications for the diagnosis and management of the disease. The introduction of breast screening, and the use of small tissue sampling for diagnosis, the recognition of new morphological and molecular subtypes, and the increasing use of neoadjuvant therapies have created challenges in pathological diagnosis and classification.Areas covered: Areas of potential difficulty include columnar cell lesions, particularly flat epithelial atypia, atypical ductal hyperplasia, lobular neoplasia and its variants, and a range of papillary lesions. Fibroepithelial, sclerosing, mucinous, and apocrine lesions are also considered. Established and newer prognostic and predictive markers, such as immune infiltrates, PD-1 and PD-L1 and gene expression assays are evaluated. The unique challenges of pathology assessment post-neoadjuvant systemic therapy are also explored.Expert opinion: Controversies in clinical management arise due to incomplete and sometimes conflicting data on clinicopathological associations, prognosis, and outcome. The review will address some of these challenges.

Microcalcifications Drive Breast Cancer Occurrence and Development by Macrophage-Mediated Epithelial to Mesenchymal Transition

BACKGROUND

This study aims to investigate: (a) the putative association between the presence of microcalcifications and the expression of both epithelial-to-mesenchymal transition and bone biomarkers, (b) the role of microcalcifications in the breast osteoblast-like cells (BOLCs) formation, and (c) the association between microcalcification composition and breast cancer progression.

METHODS

We collected 174 biopsies on which we performed immunohistochemical and ultrastructural analysis. In vitro experiments were performed to demonstrate the relationship among microcalcification, BOLCs development, and breast cancer occurrence. Ex vivo investigations demonstrated the significant increase of breast osteoblast-like cells in breast lesions with microcalcifications with respect to those without microcalcifications.

RESULTS

In vitro data displayed that in the presence of calcium oxalate and activated monocytes, breast cancer cells undergo epithelial to mesenchymal transition. Also, in this condition, cells acquired an osteoblast phenotype, thus producing hydroxyapatite. To further confirm in vitro data, we studied 15 benign lesions with microcalcification from patients that developed a malignant condition in the same breast quadrant. Immunohistochemical analysis showed macrophages' polarization in benign lesions with calcium oxalate.

CONCLUSIONS

Altogether, our data shed new light about the role of microcalcifications in breast cancer occurrence and progression.

MicroRNAs Contribute to Breast Cancer Invasiveness

Cancer statistics in 2018 highlight an 8.6 million incidence in female cancers, and 4.2 million cancer deaths globally. Moreover, breast cancer is the most frequent malignancy in females and twenty percent of these develop metastasis. This provides only a small chance for successful therapy, and identification of new molecular markers for the diagnosis and prognostic prediction of metastatic disease and development of innovative therapeutic molecules are therefore urgently required. Differentially expressed microRNAs (miRNAs) in cancers cause multiple changes in the expression of the tumorigenesis-promoting genes which have mostly been investigated in breast cancers. Herein, we summarize recent data on breast cancer-specific miRNA expression profiles and their participation in regulating invasive processes, in association with changes in cytoskeletal structure, cell-cell adhesion junctions, cancer cell-extracellular matrix interactions, tumor microenvironments, epithelial-to-mesenchymal transitions and cancer cell stem abilities. We then focused on the epigenetic regulation of individual miRNAs and their modified interactions with other regulatory genes, and reviewed the function of miRNA isoforms and exosome-mediated miRNA transfer in cancer invasiveness. Although research into miRNA’s function in cancer is still ongoing, results herein contribute to improved metastatic cancer management.

Rabbit monoclonal E-cadherin antibody: A cost-effective alternative to mouse monoclonal antibody in distinguishing ductal carcinoma in situ from lobular carcinoma in situ

Rabbit monoclonal antibody (RabMAb) demonstrates higher sensitivity without sacrificing specificity than mouse monoclonal antibody (MMAb). MMAb against E-cadherin stain is heavily utilized in distinguishing ductal carcinoma in situ (DCIS) from lobular carcinoma in situ (LCIS). We aimed to compare the E-cadherin stain using RabMAb vs MMAb in distinguishing DCIS from LCIS. One hundred and seventeen in situ breast carcinomas (55 DCIS, 58 LCIS, and 4 DCIS and LCIS) were studied. Sections from a representative block of each were stained with RabMAb [EP700Y] and MMAb [36B5]. Scanned images of stained slides were compared in tandem. All DCIS cases (59/59) showed comparable staining by RabMAb and MMAb. Comparable staining was also observed in all but one case of LCIS (61/62; 98%). One case of pleomorphic LCIS showed mostly complete, weak to moderately intense membranous staining with RabMAb and fragmented, weak membranous staining with MMAb. Consistently better staining quality was observed in slides stained by RabMAb vs MMAb. RabMAb and MMAb against E-cadherin were diagnostically equivalent with the exception of one case where RabMAb may have led to diagnostic misinterpretation. However, the not insignificant cost savings and easier interpretation using RabMAb may justify the risk of misinterpretation of increased staining in rare cases, largely avertable with proper training.

E-cadherin expression is associated with somatostatin analogue response in acromegaly

Acromegaly is a rare disease resulting from hypersecretion of growth hormone (GH) and insulin‐like growth factor 1 (IGF1) typically caused by pituitary adenomas, which is associated with increased mortality and morbidity. Somatostatin analogues (SSAs) represent the primary medical therapy for acromegaly and are currently used as first‐line treatment or as second‐line therapy after unsuccessful pituitary surgery. However, a considerable proportion of patients do not adequately respond to SSAs treatment, and therefore, there is an urgent need to identify biomarkers predictors of response to SSAs. The aim of this study was to examine E‐cadherin expression by immunohistochemistry in fifty‐five GH‐producing pituitary tumours and determine the potential association with response to SSAs as well as other clinical and histopathological features. Acromegaly patients with tumours expressing low E‐cadherin levels exhibit a worse response to SSAs. E‐cadherin levels are associated with GH‐producing tumour histological subtypes. Our results indicate that the immunohistochemical detection of E‐cadherin might be useful in categorizing acromegaly patients based on the response to SSAs.

Kernel-Based Microfluidic Constriction Assay for Tumor Sample Identification

A high-throughput multiconstriction microfluidic channels device can distinguish human breast cancer cell lines (MDA-MB-231, HCC-1806, MCF-7) from immortalized breast cells (MCF-10A) with a confidence level of ∼81-85% at a rate of 50-70 cells/min based on velocity increment differences through multiconstriction channels aligned in series. The results are likely related to the deformability differences between nonmalignant and malignant breast cells. The data were analyzed by the methods/algorithms of Ridge, nonnegative garrote on kernel machine (NGK), and Lasso using high-dimensional variables, including the cell sizes, velocities, and velocity increments. In kernel learning based methods, the prediction values of 10-fold cross-validations are used to represent the difference between two groups of data, where a value of 100% indicates the two groups are completely distinct and identifiable. The prediction value is used to represent the difference between two groups using the established algorithm classifier from high-dimensional variables. These methods were applied to heterogeneous cell populations prepared using primary tumor and adjacent normal tissue obtained from two patients. Primary breast cancer cells were distinguished from patient-matched adjacent normal cells with a prediction ratio of 70.07%-75.96% by the NGK method. Thus, this high-throughput multiconstriction microfluidic device together with the kernel learning method can be used to perturb and analyze the biomechanical status of cells obtained from small primary tumor biopsy samples. The resultant biomechanical velocity signatures identify malignancy and provide a new marker for evaluation in risk assessment.