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

Pleomorphic Lobular Carcinoma In Situ Composed of Signet-Ring Cells Mimicking Ductal Carcinoma In Situ with A Papillary Pattern: A Case Report

While some forms of invasive or in situ carcinoma of the breast may be partly composed of signet-ring cells, signet-ring cells rarely become a prominent feature of pleomorphic lobular carcinoma in situ (LCIS). We report a rare example of pleomorphic LCIS composed predominantly of signet-ring cells with a papillary pattern mimicking ductal carcinoma in situ (DCIS). A 58-year-old woman presented with a mass in the left breast detected by ultrasonography. Fourteen years previously, the patient underwent right breast-conserving surgery for invasive breast carcinoma of no special type. Ultrasonography revealed an irregular parallel, angular hypoechoic mass measuring 1.5 cm in the left breast. An ultrasound-guided core needle core biopsy was conducted. Microscopically, the lesion was composed of epithelial cells supported by a fibrovascular stroma. The majority (> 70%) of the lesional cells between the fibrovascular stalks showed signet-ring cell features. Some of the nuclei of the signet-ring cells showed intermediate-grade atypia. A mucicarmine stain showed intracytoplasmic mucin in the signet-ring cells. Immunohistochemistry for E-cadherin was negative in the tumor cells. After surgical excision, the final diagnosis was a pleomorphic LCIS. To our knowledge, there have been no previous reports of pleomorphic LCIS consisting primarily of signet-ring cells with a papillary pattern.

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.

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.

Protein biomarkers for subtyping breast cancer and implications for future research: a 2024 update

INTRODUCTION

Breast cancer subtyping is used clinically for diagnosis, prognosis, and treatment decisions. Subtypes are categorized by cell of origin, histomorphology, gene expression signatures, hormone receptor status, and/or protein levels. Categorizing breast cancer based on gene expression signatures aids in assessing a patient's recurrence risk. Protein biomarkers, on the other hand, provide functional data for selecting therapies for primary and recurrent tumors. We provide an update on protein biomarkers in breast cancer subtypes and their application in prognosis and therapy selection.

AREAS COVERED

Protein pathways in breast cancer subtypes are reviewed in the context of current protein-targeted treatment options. PubMed, Science Direct, Scopus, and Cochrane Library were searched for relevant studies between 2017 and 17 August 2024.

EXPERT OPINION

Post-translationally modified proteins and their unmodified counterparts have become clinically useful biomarkers for defining breast cancer subtypes from a therapy perspective. Tissue heterogeneity influences treatment outcomes and disease recurrence. Spatial profiling has revealed complex cellular subpopulations within the breast tumor microenvironment. Deciphering the functional relationships between and within tumor clonal cell populations will further aid in defining breast cancer subtypes and create new treatment paradigms for recurrent, drug resistant, and metastatic disease.

Immediate and delayed risk of breast cancer associated with classic lobular carcinoma in situ and its variants

OBJECTIVE

To determine the risk of breast cancer due to lobular carcinoma in situ (LCIS).

METHODS

This retrospective IRB-approved study identified cases of LCIS after percutaneous breast biopsy from 7/2005 to 7/2022. Excluded were cases with less than 2 years of imaging surveillance or a concurrent ipsilateral breast cancer diagnosis within 6 months of the LCIS diagnosis. Final outcomes of cancer versus no cancer were determined by pathology at surgical excision or the absence of cancer on imaging surveillance.

RESULTS

A total of 116 LCIS lesions were identified. The primary imaging findings targeted for percutaneous biopsy included calcifications (50.0%, 58/116), MR enhancing lesions (25.0%, 29/116), noncalcified mammographic architectural distortions (10.3%, 12/116), or masses (14.7%, 17/116). Surgical excision was performed in 49.1% (57/116) and imaging surveillance was performed in 50.9% (59/116) of LCIS cases. There were 22 cancers of which 11 cancers were discovered at immediate excision [19.3% (11/57) immediate upgrade] and 11 cancers developed later while on imaging surveillance [18.6% (11/59) delayed risk for cancer]. Among all 22 cancers, 63.6% (14/22) occurred at the site of LCIS (11 at immediate excision and 3 at surveillance) and 36.4% (8/22) occurred at a location away from the site of LCIS (6 in a different quadrant and 2 in the contralateral breast).

CONCLUSION

LCIS has both an immediate risk (19.3%) and a delayed risk (18.6%) for cancer with 90.9% occurring in the ipsilateral breast (63.6% at and 27.3% away from the site of LCIS) and 9.1% occurring in the contralateral breast.

Upgrade Rates of Variant Lobular Carcinoma In Situ Compared to Classic Lobular Carcinoma In Situ Diagnosed in Core Needle Biopsies: A 10-Year Single Institution Retrospective Study

The primary aim of this study was to determine the upgrade rates of variant lobular carcinoma in situ (V-LCIS, ie, combined florid [F-LCIS] and pleomorphic [P-LCIS]) compared with classic LCIS (C-LCIS) when diagnosed on core needle biopsy (CNB). The secondary goal was to determine the rate of progression/development of invasive carcinoma on long-term follow-up after primary excision. After institutional review board approval, our institutional pathology database was searched for patients with "pure" LCIS diagnosed on CNB who underwent subsequent excision. Radiologic findings were reviewed, radiologic-pathologic (rad-path) correlation was performed, and follow-up patient outcome data were obtained. One hundred twenty cases of LCIS were identified on CNB (C-LCIS = 97, F-LCIS = 18, and P-LCIS = 5). Overall upgrade rates after excision for C-LCIS, F-LCIS, and P-LCIS were 14% (14/97), 44% (8/18), and 40% (2/5), respectively. Of the total cases, 79 (66%) were deemed rad-path concordant. Of these, the upgrade rate after excision for C-LCIS, F-LCIS, and P-LCIS was 7.5% (5 of 66), 40% (4 of 10), and 0% (0 of 3), respectively. The overall upgrade rate for V-LCIS was higher than for C-LCIS (P = .004), even for the cases deemed rad-path concordant (P value: .036). Most upgraded cases (23 of 24) showed pT1a disease or lower. With an average follow-up of 83 months, invasive carcinoma in the ipsilateral breast was identified in 8/120 (7%) cases. Six patients had died: 2 of (contralateral) breast cancer and 4 of other causes. Because of a high upgrade rate, V-LCIS diagnosed on CNB should always be excised. The upgrade rate for C-LCIS (even when rad-path concordant) is higher than reported in many other studies. Rad-path concordance read, surgical consultation, and individualized decision making are recommended for C-LCIS cases. The risk of developing invasive carcinoma after LCIS diagnosis is small (7% with ∼7-year follow-up), but active surveillance is required to diagnose early-stage disease.

Does Non-Classic Lobular Carcinoma In Situ at the Lumpectomy Margin Increase Local Recurrence?

BACKGROUND

The clinical significance of nonclassic, lobular carcinoma in situ (NC-LCIS) at the surgical margin of excisions for invasive cancer is unknown. We sought to determine whether NC-LCIS at or near the margin in the setting of a concurrent invasive carcinoma is associated with risk of ipsilateral breast tumor recurrence (IBTR) and locoregional recurrence (LRR).

METHODS

Patients with stage 0-III breast cancer and NC-LCIS who underwent lumpectomy between January 2010 and January 2022 at a single institution were retrospectively identified. NC-LCIS margins were stratified as <2 mm, ≥2 mm, or within shave margin. Rates of IBTR and LRR were examined.

RESULTS

A total of 511 female patients (median age 60 years [interquartile range (IQR) 52-69]) with NC-LCIS and an associated ipsilateral breast cancer with a median follow-up of 3.4 years (IQR 2.0-5.9) were identified. Final margins for NC-LCIS were ≥2 mm in 348 patients (68%), <2 mm in 37 (7.2%), and within shave margin in 126 (24.6%). Crude incidence of IBTR was 3.3% (n = 17) and that of LRR was 4.9% (n = 25). There was no difference in the crude rate of IBTR by NC-LCIS margin status (IBTR rate: 3.7% ≥2 mm, 0% <2 mm, 3.2% within shave margin, p = 0.8) nor in LRR (LRR rate: 4.9% ≥2 mm, 2.7% <2 mm, 5.6% within shave margin, p = 0.9).

CONCLUSIONS

For completely excised invasive breast cancers associated with NC-LCIS, extent of margin width for NC-LCIS was not associated with a difference in IBTR or LRR. These data suggest that the decision to perform reexcision of margin after lumpectomy should be driven by the invasive cancer, rather than the NC-LCIS margin.

Management of Lobular Neoplasia Diagnosed by Core Biopsy

Lobular neoplasia (LN) involves proliferative changes within the breast lobules. LN is divided into lobular carcinoma in situ (LCIS) and atypical lobular hyperplasia (ALH). LCIS can be further subdivided into three subtypes: classic LCIS, pleomorphic LCIS, and LCIS with necrosis (florid type). Because classic LCIS is now considered as a benign etiology, current guidelines recommend close follow-up with imaging versus surgical excision. The goal of our study was to determine if the diagnosis of classic LN on core needle biopsy (CNB) merits surgical excision. This is a retrospective, observational study conducted at Mount Auburn Hospital, Cambridge, MA, from May 17, 2017, through June 30, 2020. We reviewed the data of breast biopsies conducted at our hospital over this period and included patients who were diagnosed with classic LN (LCIS and/or ALH) and excluded patients having any other atypical lesions on CNB. All known cancer patients were excluded. Of the 2707 CNBs performed during the study period, we identified 68 women who were diagnosed with ALH or LCIS on CNB. CNB was performed for an abnormal mammogram in the majority of patients (60; 88%) while 7(10.3%) had an abnormal breast magnetic resonance imaging study (MRI), and 1 had an abnormal ultrasound (US). A total of 58 patients (85%) underwent excisional biopsy, of which 3 (5.2%) showed malignancy, including 2 cases of DCIS and 1 invasive carcinoma. In addition, there was 1 case (1.7%) with pleomorphic LCIS and 11 cases with ADH (15.5%). The management of LN found on core biopsy is evolving, with some advocating surgical excision and others recommending observation. Our data show a change in diagnosis with excisional biopsy in 13 (22.4%) of patients with 2 cases of DCIS, 1 invasive carcinoma, 1 pleomorphic LCIS, and 9 cases of ADH, diagnosed on excisional biopsy. While ALH and classic LCIS are considered benign, the choice of ongoing surveillance versus excisional biopsy should be made with shared decision making with the patient, with consideration of personal and family history, as well as patient preferences.

Presence of Non-classic LCIS Is Not a Contraindication to Breast Conservation in Patients with Concomitant Invasive Breast Cancer or DCIS

BACKGROUND

Non-classic lobular carcinoma in situ (NC-LCIS) represents a spectrum of lesions, histologically distinct from classic LCIS (C-LCIS) and ductal carcinoma in situ (DCIS). Several studies have reported on the safety of breast conservation (BCS) in patients with DCIS or invasive breast cancer and concomitant C-LCIS, yet there are no data addressing this question for patients with concomitant NC-LCIS. We evaluated local recurrence (LR) after BCS in patients with DCIS or invasive cancer and concomitant NC-LCIS.

PATIENTS AND METHODS

We searched institutional databases using natural language processing to identify patients with DCIS or invasive breast cancer and concomitant NC-LCIS treated with BCS between 2000 and 2015. Charts were reviewed to collect demographics, disease and treatment details, and recurrence events. All results represent descriptive analyses.

RESULTS

We identified 71 patients with DCIS (n = 13) or invasive cancer (n = 58) and concomitant NC-LCIS treated with BCS. Median patient age was 59 years (33-77 years), and median invasive tumor size was 1.2 cm (0.1-6.9 cm); 62% of DCIS and 79% of invasive cancer patients had hormone receptor (HR)-positive disease. Among DCIS patients, seven (54%) received radiation and none hormonal therapy. Among those with invasive cancer, 52 (90%) received radiation, 17 (29%) received chemotherapy and 44 of 55 with HR-positive disease (78%) received hormonal therapy. At median follow-up of 79 months (1-265 months), the LR rate was 8% and 2% among patients with DCIS and invasive cancer, respectively.

CONCLUSION

NC-LCIS is rarely present in association with DCIS or invasive cancer, and it does not appear to impact LR outcomes following BCS.

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.

[Updated WHO classification of tumors of the breast]

In the fifth edition of the World Health Organization (WHO) classification of tumors of the breast, the histological features of the lesions continue to form the basis of the classification; however, molecular pathology nowadays provides approaches for improved diagnostics and prediction of prognosis and treatment response, which have been incorporated into the update of the classification. The most important changes are presented, which include changes in the histological classification of invasive carcinomas, the subtyping of lobular carcinoma in situ (LCIS) and the dignity criteria of phyllodes tumors.

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.

[Updated WHO classification of tumors of the breast: the most important changes]

The development of the WHO classification of tumors of the breast is driven by new knowledge from research whose translation into daily practice is considered clinically relevant. The fifth edition represents an update of the fourth edition and essentially follows the previously known systematics. The histologic features of the lesions continue to form the basis of the classification in the update. This also applies to the definition of invasive tumor types. However, several new molecular classifications as well as additional prognostic and predictive factors are presented and discussed, which improve prognosis estimation and therapy decisions. This paper aims to present the main changes in the current WHO classification. These include the revised definition of mixed invasive carcinomas, the introduction of new special invasive entities (tall cell carcinoma with reversed polarity, mucinous cystadenocarcinoma), the deletion of special invasive types and their classification as variants of invasive carcinoma, NST (no special type, including medullary, lipid-rich, glycogen-rich, among others), the typing of primary neuroendocrine neoplasms of the breast by analogy with other organ systems, changes in the dignity criteria of phyllodes tumors, and the revised subtyping of lobular carcinoma in situ (LCIS). In addition to improvements in the fifth edition of the classification, flaws are also highlighted. A section is devoted to new molecular parameters.

Invasive lobular carcinoma of the breast: the increasing importance of this special subtype

Invasive lobular carcinoma (ILC) is the most common of the breast cancer special types, accounting for up to 15% of all breast cancer cases. ILCs are noted for their lack of E-cadherin function, which underpins their characteristic discohesive growth pattern, with cells arranged in single file and dispersed throughout the stroma. Typically, tumours are luminal in molecular subtype, being oestrogen and progesterone receptor positive, and HER2 negative. Since last reviewing the lobular literature (McCart Reed et al., Breast Cancer Res 17:12, 2015), there has been a considerable increase in research output focused on this tumour type, including studies into the pathology and management of disease, a high-resolution definition of the genomic landscape of tumours as well as the evolution of several potential therapeutic avenues. There abounds a huge amount of new data, which we will review herein.

Lobular carcinoma in situ: diagnostic criteria and molecular correlates

Lobular neoplasia (LN) is an atypical proliferation of small, dyscohesive epithelial cells within the terminal duct lobular unit (TDLU), with or without pagetoid extension and encompasses both lobular carcinoma in situ (LCIS) and atypical lobular hyperplasia (ALH). LN is a non-obligate precursor of invasive breast carcinoma and the diagnosis of LN confers an increased risk of invasive carcinoma development, compared to the general population. Diagnostic challenges arise in the accurate classification of LCIS into classic, pleomorphic and florid subtypes, in distinguishing between LCIS and ductal carcinoma in situ (DCIS) and in the appropriate use and interpretation of E-cadherin immunohistochemistry. Due to the paucity of robust data on the natural history of LCIS, and hence its clinical significance, the management is often pragmatic rather than entirely evidence-based and requires a multidisciplinary approach. In this review, we discuss the clinicopathologic and molecular features of LCIS and address the key challenges that arise in the diagnosis and management of LCIS.

Precision pathology as applied to breast core needle biopsy evaluation: implications for management

With the shift to de-escalation of therapy for some breast cancers and fewer surgical excisions for high-risk lesions identified on breast imaging studies at one end of the spectrum, and the greater use of neoadjuvant systemic therapy at the other end, pathologists are ever more critical in guiding management decisions for women with breast disease following core needle biopsy. One important consequence of this shift in management paradigms is the elimination of the opportunity for a "second-look" with the excision specimen to confirm or refine the diagnosis rendered on core needle biopsy. Thus, not only is there the imperative for accuracy and precision of core needle biopsy diagnoses, increasingly it is the only opportunity for that diagnosis.