Apocrine carcinoma of the breast: A brief update on the molecular features and targetable biomarkers

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.

Clinicopathologic and Immunophenotypic Classification of Invasive Lobular Carcinoma with Histiocytoid Features

INTRODUCTION

Histiocytoid lobular breast carcinoma is a rare subtype of invasive lobular carcinoma characterized by relatively bland, uniform nuclei, single small eosinophilic nucleolus, and ample granular cytoplasm. These cancers are typically triple negative, show frequent androgen receptor (AR) positivity, and are therefore theorized to represent a variant of apocrine differentiation in invasive lobular carcinoma. Anecdotal evidence suggests that these tumors have excellent outcomes, though some studies suggest a variable clinical outcome.

METHODS

Inclusion criteria included women with a histologic diagnosis of invasive lobular carcinoma with histiocytoid features, regardless of immunohistochemical profile, diagnosed at our institution between 2008 and 2021 with additional tissue still available for ancillary studies. We reviewed patients meeting these criteria and investigated hematoxylin and eosin-stained slides and a panel of immunohistochemical stains (estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 [HER2], AR, endothelial growth factor receptor, and keratin 5/6), as well as outcomes including survival and metastatic disease.

RESULTS

Overall, 12 eligible patients were identified. The classical immunophenotype (triple negative with AR positivity) was noted in 4 out of 12 tumors. The majority of the remaining tumors (7 out of 12) showed a luminal B immunohistochemical profile, while 1 out of 12 was HER2-enriched. No patients in the cohort died from disease-related causes and 2 out of 12 presented with distant metastatic disease during their disease course.

CONCLUSION

Histiocytoid lobular breast carcinoma is a morphologic variant of lobular carcinoma with apocrine features that shows a variable immunohistochemical profile and variable clinical behavior. Further subclassification and stricter diagnostic criteria may be helpful in the distinction between truly indolent tumors and those with more aggressive clinical features.

The assessment of tumor-infiltrating lymphocytes in invasive apocrine carcinoma of the breast in relation to the HER2 status

In the current study, we assessed the prevalence and molecular features of HER2-low phenotype in the apocrine carcinomas of the breast (ApoCa) and its relationship with tumor-infiltrating lymphocytes (TILs). A cohort of 64 well-characterized therapy-naïve ApoCa was used. The TIL distribution was assessed using the hematoxylin and eosin whole slide/scanned images following the international TILs working group recommendations. Next-generation sequencing (NGS) was performed in a subset of HER2-low ApoCa. All patients were women, with a mean age of 62 years. Forty-three carcinomas were pure apocrine carcinoma (PAC; ER-/AR+), and the remaining 21 were classified as apocrine-like carcinomas (ALCs; ER+/-, AR+/-). HER2/neu was positive (score 3+ by IHC and/or amplified by FISH) in 20/43 (47%) PAC and 4/21 (19%) ALC. The prevalence of HER2-low expression (scores 1+ or 2+ without HER2 amplification) in ApoCa was 39% without significant differences between PAC and ALC (P = 0.14); however, the HER2-low phenotype was more prevalent in triple-negative PAC than in ALC (P < 0.001). Levels of TILs were low (≤10%) in 74% of ApoCa (median 5%, range 0%-50%). TIL levels were significantly higher in ALC than in PAC (P = 0.02). HER2 status had no impact on TIL distribution (P = 0.45). The genomic profile of HER2-low ApoCa was similar to other subtypes of ApoCa. ApoCa has predominantly low TIL, particularly PAC. The prevalence of the HER2-low phenotype in ApoCa is high, which should have therapeutic and clinical implications given the recently approved therapies with antibody-drug conjugates (ADCs) for HER2-low breast cancers.

Novel immunotherapies for breast cancer: Focus on 2023 findings

Immunotherapy has emerged as a revolutionary approach in cancer therapy, and recent advancements hold significant promise for breast cancer (BCa) management. Employing the patient's immune system to combat BCa has become a focal point in immunotherapeutic investigations. Strategies such as immune checkpoint inhibitors (ICIs), adoptive cell transfer (ACT), and targeting the tumor microenvironment (TME) have disclosed encouraging clinical outcomes. ICIs, particularly programmed cell death protein 1 (PD-1)/PD-L1 inhibitors, exhibit efficacy in specific BCa subtypes, including triple-negative BCa (TNBC) and human epidermal growth factor receptor 2 (HER2)-positive cancers. ACT approaches, including tumor-infiltrating lymphocytes (TILs) and chimeric antigen receptor (CAR) T-cell therapy, showed promising clinical outcomes in enhancing tumor recognition and elimination. Targeting the TME through immune agonists and oncolytic viruses signifies a burgeoning field of research. While challenges persist in patient selection, resistance mechanisms, and combination therapy optimization, these novel immunotherapies hold transformative potential for BCa treatment. Continued research and clinical trials are imperative to refine and implement these innovative approaches, paving the way for improved outcomes and revolutionizing the management of BCa. This review provides a concise overview of the latest immunotherapies (2023 studies) in BCa, highlighting their potential and current status.

A Preliminary Investigation into Search and Matching for Tumor Discrimination in World Health Organization Breast Taxonomy Using Deep Networks

Breast cancer is one of the most common cancers affecting women worldwide. It includes a group of malignant neoplasms with a variety of biological, clinical, and histopathologic characteristics. There are more than 35 different histologic forms of breast lesions that can be classified and diagnosed histologically according to cell morphology, growth, and architecture patterns. Recently, deep learning, in the field of artificial intelligence, has drawn a lot of attention for the computerized representation of medical images. Searchable digital atlases can provide pathologists with patch-matching tools, allowing them to search among evidently diagnosed and treated archival cases, a technology that may be regarded as computational second opinion. In this study, we indexed and analyzed the World Health Organization breast taxonomy (Classification of Tumors fifth ed.) spanning 35 tumor types. We visualized all tumor types using deep features extracted from a state-of-the-art deep-learning model, pretrained on millions of diagnostic histopathology images from the Cancer Genome Atlas repository. Furthermore, we tested the concept of a digital "atlas" as a reference for search and matching with rare test cases. The patch similarity search within the World Health Organization breast taxonomy data reached >88% accuracy when validating through "majority vote" and >91% accuracy when validating using top n tumor types. These results show for the first time that complex relationships among common and rare breast lesions can be investigated using an indexed digital archive.

Multiomic analysis of HER2-enriched and AR-positive breast carcinoma with apocrine differentiation and an oligometastatic course: a case report

Breast carcinoma is the most prevalent cancer among women globally. It has variable clinical courses depending on the stage and clinical-biological features. This case report describes a 56-year-old female with invasive breast cancer without estrogen or progesterone receptor expression, with apocrine differentiation, and with no germline variants in the BRCA1 and BRCA2 genes. Throughout the clinical course, the patient exhibited discordant results for HER2 in immunohistochemistry and in situ hybridization. During the second relapse, the disease displayed apocrine microscopic features. The tumor underwent analysis for the androgen receptor, GCDFP-15, RNA-seq, and whole-genome sequencing (WGS) to identify the breast cancer subtype and to characterize the cancer genome. Our bioinformatic analysis revealed 20,323 somatic SNV/Indels, including five mutations in cancer-related genes that are believed to be responsible for the tumor's development. Two of these mutations were found in the PIK3CA and TP53 genes. Furthermore, the tumor tissue exhibited large copy number alterations to the chromosomes, which could impact gene expression through complex mechanisms and contribute to the tumor phenotype. Clustering algorithms applied on RNA-sequencing data categorized this cancer as a HER2+ subtype. The second-line capecitabine chemotherapy treatment is ongoing, and the patient is responding well. Bioinformatic results support the current treatment decision and open the way to further treatments.

Apocrine adenocarcinoma of the breast: A rare special subtype with divergent theranostic markers

Carcinoma of the breast with apocrine differentiation also known as apocrine adenocarcinomas is special histological subtypes comprising approximately 1% of breast cancers. They are estrogen receptor/progesterone receptor-negative and androgen receptor-positive tumors having more than 90% population of tumor cells with apocrine morphology. We present a 49-year-old woman with a breast lump in the right upper outer quadrant clinically and radiologically diagnosed as malignancy and histologically proven as apocrine adenocarcinoma of the breast owing to the morphology comprising tumor cells having abundant granular cytoplasm, central to the eccentric nucleus and prominent nucleoli. On immunohistochemistry, it was a triple-negative tumor with AR positivity. As apocrine adenocarcinoma of the breast has an uncertain prognosis, variable HER2/neu overexpression, debatable responses to neoadjuvant therapy, and probable response to androgen therapy, the onus of diagnosing and reporting these tumors accurately lies with the pathologist. Moreover, as the presentation of these tumors is similar to invasive breast carcinoma, no special type but with potentially different and useful theranostic markers, an emphasis on specifying this histological subtype is becoming increasingly essential.

Acinic cell carcinoma of the breast: A comprehensive review

Acinic cell carcinoma of the breast is a rare special subtype of breast cancer in the category of salivary gland-type tumors. It is morphologically similar to acinic cell carcinomas of salivary glands and pancreas and has a triple-negative phenotype (estrogen receptor-negative, progesterone receptor-negative, and Her-2/neu negative). Its molecular genomic features are more similar to triple-negative breast cancer of no special type than to its salivary gland counterpart. However, the clinical course of the mammary acinic cell carcinoma appears to be less aggressive than the usual triple-negative breast carcinomas. This review comprehensively summarizes the current literature on the clinicopathologic, immunohistochemical, and molecular features of this rare and distinct subtype of breast cancer.

Relationship of Tubule Formation, Indian File Pattern and Apocrine Change With Estrogen and Progesterone Receptors and HER2 Immunostaining

Objectives: In breast carcinomas, histomorphological features like low-grade and lobular differentiation are associated with estrogen receptor (ER) and progesterone receptor (PR) expression. Apocrine carcinoma is associated with human epidermal growth factor receptor 2 (HER2) positivity. Studies have not emphasized the association between other histological features like tubule formation, Indian file pattern and apocrine change (which may be found in all grades of tumors or as a part of a mixed pattern of no special type) and immunohistochemistry (IHC). The study was designed to find the association between these morphological factors and ER, PR and HER2 status.

Materials and methods: The presence or absence of tubule formation, Indian file pattern and apocrine change was correlated with ER, PR and HER2 expression in core biopsies of 102 invasive breast carcinomas.

Statistical analysis: Fisher exact test with median unbiased odds ratio was used.

Results: Tubule formation and/or Indian file pattern were significantly associated with ER in all tumors (P-value <0.001), as well as separately for grade II, grade III, HER2-negative and HER2-positive tumors. Comparable results were obtained for their association with PR. Apocrine change was significantly associated with HER2 in all tumors (P-value <0.001), as well as separately for grade III, ER-positive and ER-negative tumors.

Conclusion: These histomorphological patterns are modest predictors of IHC status in breast carcinomas, even in tumors of higher grade. Knowledge of these morphological correlates of ER, PR and HER2 in breast cancer may serve as an aid in the quality management of breast carcinoma reporting.

Nomogram for predicting overall survival in patients with triple-negative apocrine breast cancer: Surveillance, epidemiology, and end results-based analysis

PURPOSE

Triple-negative apocrine carcinoma (TNAC) is a sort of triple-negative breast cancer (TNBC) that is rare and prognosis of these patients is unclear. The present study constructed an effective nomogram to assist in predicting TNAC patients overall survival (OS).

METHODS

A total of 373 TNAC patients from the surveillance, epidemiology, and end results (SEER) got extracted from 2010 to 2016 and were divided into training (n = 261) and external validation (n = 112) groups (split ratio, 7:3) randomly. A Cox regression model was utilized to creating a nomogram according to the risk factors affecting prognosis. The predictive capability of the nomogram was estimated with receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA).

RESULTS

Multivariate Cox regression analysis revealed age, surgery, chemotherapy, stage, and first malignant primary as independent predictors of OS. A prediction model was constructed and virtualized using the nomogram. The time-dependent area under the curve (AUC) showed satisfactory discrimination of the nomogram. Good consistency was shown on the calibration curves in OS between actual observations and the nomogram prediction. What's more, DCA showed that the nomogram had incredible clinical utility. Through separating the patients into groups of low and high risk group that connects with the risk system that shows a huge difference between the low-risk and high risk OS (P < 0.001).

CONCLUSION

To predict the OS in TNAC patients, the nomogram utilizing the risk stratification system that is corresponding. These tools may help to evaluate patient prognosis and guide treatment decisions.

HER2-positive apocrine carcinoma of the breast: a population-based analysis of treatment and outcome

PURPOSE

Apocrine carcinoma of the breast (APO) expresses HER2 in 30-50% of cases. This study explored the clinicopathological features and outcome of HER2+/APO and matched HER2+/NST cohort.

METHODS

We used the SEER database to explore the cohorts. Univariate and multivariate analyses were used to assess the survival. Based on ER and PR [steroid receptors/SR/] and HER2 status, we divided the cohorts to match the intrinsic molecular subtypes for comparisons.

RESULTS

We retrieved 259 cases of HER2+/APO. Most HER2+/APO were SR negative (65%). HER2+/APO were more prevalent in the 80+ age group (24.7% vs. 15.7%, p < 0.001). HER2+/SR-/APO had a significantly lower histological grade than the HER2+/SR-/NST (p < 0.001). Breast cancer-related deaths were more prevalent in HER2+/NST (7.8% vs. 3.9%, p = 0.019). This was particularly evident between SR- subgroups (10.4% in HER2+/SR-/NST vs. 4.2% in HER2+/SR-/APO, p = 0.008) and was reaffirmed in breast cancer-specific survival in univariate analysis (p = 0.03). Other than race and SR status, HER2+/APO subgroups did not differ in clinicopathological parameters.

CONCLUSIONS

Our study confirms the rarity of the APO and reveals that SR status in APO does not affect these patients' prognosis. HER2+/APO tumors tend to have a less aggressive phenotype and a more favorable outcome despite a markedly lower ER/PR positivity.

An Update on the Molecular and Clinical Characteristics of Apocrine Carcinoma of the Breast

Apocrine carcinoma of the breast is a rare malignancy. According to 2019 WHO classification, apocrine cellular features and a characteristic steroid receptor profile (Estrogen receptor (ER)-negative and androgen receptor (AR)-positive) define apocrine carcinoma. Her-2/neu protein expression is reported in ∼30-50% of apocrine carcinomas, while NGS analysis showed frequent PIK3CA/PTEN/AKT and TP53 mutations Followed by deregulation in the mitogen-activated protein kinase pathway components (mutations of KRAS, NRAS, BRAF). A recent miRNA study indicates various miRNAs (downregulated hsa-miR-145-5p and upregulated 14 miRNAs such as hsa-miR-182-5p, hsa-miR-3135b, and hsa-miR-4417) may target the commonly altered pathways in apocrine carcinomas such as ERBB2/HER2 and mitogen-activated protein kinase signaling pathway. Although AR expression is a hallmark of apocrine carcinoma, little is known regarding the efficacy/resistance to antiandrogens. Success of bicalutamide, a non-steroidal anti-androgen, was reported in a case of Her2-negative apocrine carcinoma. Two recent studies, however, described presence of anti-androgen resistance biomarkers (a splice variant ARv7 and AR/NCOA2 co-amplification) in a subset of AR+ apocrine carcinomas, cautioning the use of anti-androgens in AR+ triple-negative breast carcinomas. Apocrine carcinomas rarely show biomarkers predictive of response to immune checkpoint inhibitors (PD-L1 expression, MSI-H status, and TMB-high). Therefore, a comprehensive cancer profiling of apocrine carcinomas is necessary to identify potential therapeutic targets for a truly individualized treatment approach.

Breast Apocrine Carcinoma Detected Incidentally as Axillary Lymphadenopathy in a CT Scan

Breast apocrine cell pathology varieties include benign papilloma, non-high-grade apocrine ductal carcinoma in situ (DCIS), and breast invasive apocrine carcinoma (BAC). BAC is a rare type of invasive breast cancer and is histologically distinguished by large-sized cells with copious eosinophilic granular cytoplasm, round nuclei, and prominent nucleoli. Its prognosis is similar to breast invasive ductal carcinoma, of no special type (IDC-NST), when matched for tumour stage and histological grade. In this paper, we report the case of a 75-year-old lady presenting with apocrine carcinoma of the left breast diagnosed at the stage of mediastinal lymph node metastasis.

Apocrine lesions of the breast

Apocrine change is recognised in benign, atypical and malignant lesions of the breast. Apocrine metaplasia, a frequent finding in the breast of women over the age of 25 years, is most commonly seen in benign cysts with a simple or papillary configuration. Apocrine change is also recognised in other benign lesions including sclerosing adenosis, now known as apocrine adenosis. Apocrine atypia usually refers to cytological atypia in which there is at least threefold variation in nuclear size but architectural atypia may also occur. The distinction between atypical apocrine hyperplasia and non-high-grade apocrine ductal carcinoma in situ may be difficult due to the relative rarity of these entities and the lack of validated diagnostic criteria. Lobular carcinoma in situ (LCIS) with apocrine change is considered to be a variant of pleomorphic LCIS. An apocrine variant of encapsulated papillary carcinoma is also recognised. Apocrine change is described in invasive carcinoma, including no special type, lobular, micropapillary and mucinous variants. The recent WHO 2019 update recognises 'carcinoma with apocrine differentiation' as a special type breast carcinoma based on the presence of apocrine morphology in at least 90% of the tumour. Tumours with apocrine morphology are usually but not always hormone receptor negative. Human epidermal growth factor receptor 2 (HER-2) status is variable. Molecular studies have identified breast tumours with apocrine features and high expression of androgen receptor mRNA including 'luminal androgen receptor tumours' and 'molecular apocrine tumours'. The term 'pure apocrine carcinoma' has been proposed to describe an invasive carcinoma with apocrine morphology that is oestrogen and progesterone receptor negative and androgen receptor positive. HER-2 status may be positive or negative. This article reviews the pathology of benign, atypical and malignant apocrine lesions of the breast, with emphasis on diagnostic criteria including an approach to evaluation of apocrine lesions on needle core biopsy, and recent advances in our understanding of invasive apocrine carcinoma.

Histology of Luminal Breast Cancer

Background

Invasive breast cancer (IBC) can be categorized into prognostic and predictive molecular subtypes (including luminal breast cancer) using gene expression profiling. Luminal IBC comprises a variety of histological subtypes with varying clinical and pathological features.

Summary

IBC of no special subtype is the most common histological subtype in general and likewise within luminal IBC. Classical invasive lobular breast cancer, typically clustering into luminal subgroup, is characterized by discohesive growth and loss of E-cadherin expression. Infrequent, morphologically distinct luminal IBC subtypes are tubular, invasive cribriform, mucinous, and invasive micropapillary carcinomas. Breast carcinoma with apocrine differentiation, with characteristic expression of androgen receptor (AR), often clusters into the luminal AR category. Rarely, neuroendocrine neoplasms of the breast can be seen. IBC of the male breast usually matches with the luminal subtype.

Key Messages

Independently from histological subtypes, invasive breast cancer (IBC) can be divided into molecular subtypes based on mRNA gene expression levels. Using this molecular subtyping, risk scores based on gene expression profiling (established for hormone receptor-positive, HER2-negative IBC), grading, and Ki-67 index, prognosis of patients with luminal breast cancer and response to chemotherapy can be predicted. In routine diagnostics, the expression of estrogen receptor (ER) and progesterone receptor (PR), HER2 status, and the proliferation rate (Ki-67) are used to determine a surrogate (molecular-like) subtype. Within luminal(-like) IBC, no special subtype and invasive lobular breast carcinoma are the most common histological subtypes. Other rare histological subtypes (e.g., tubular carcinoma) should be recognized due to their distinct clinical and pathological features.

Histologic subtyping affecting outcome of triple negative breast cancer: a large Sardinian population-based analysis

BACKGROUND

Triple Negative breast cancer (TNBC) includes a heterogeneous group of tumors with different clinico-pathological features, molecular alterations and treatment responsivity. Our aim was to evaluate the clinico-pathological heterogeneity and prognostic significance of TNBC histologic variants, comparing "special types" to high-grade invasive breast carcinomas of no special type (IBC-NST).

METHODS

This study was performed on data obtained from TNBC Database, including pathological features and clinical records of 1009 TNBCs patients diagnosed between 1994 and 2015 in the four most important Oncology Units located in different hospitals in Sardinia, Italy. Kaplan-Meier analysis, log-rank test and multivariate Cox proportional-hazards regression were applied for overall survival (OS) and disease free survival (DFS) according to TNBC histologic types.

RESULTS

TNBC "special types" showed significant differences for several clinico-pathological features when compared to IBC-NST. We observed that in apocrine carcinomas as tumor size increased, the number of metastatic lymph nodes manifestly increased. Adenoid cystic carcinoma showed the smallest tumor size relative to IBC-NST. At five-year follow-up, OS was 92.1, 100.0, and 94.5% for patients with apocrine, adenoid cystic and medullary carcinoma, respectively; patients with lobular and metaplastic carcinoma showed the worst OS, with 79.7 and 84.3%, respectively. At ten-years, patients with adenoid cystic (100.0%) and medullary (94.5%) carcinoma showed a favourable prognosis, whereas patients with lobular carcinoma showed the worst prognosis (73.8%). TNBC medullary type was an independent prognostic factor for DFS compared to IBC-NST.

CONCLUSIONS

Our study confirms that an accurate and reliable histopathologic definition of TNBC subtypes has a significant clinical utility and is effective in the therapeutic decision-making process, with the aim to develop innovative and personalized treatments.

Crosstalk between HER2 and PD-1/PD-L1 in Breast Cancer: From Clinical Applications to Mathematical Models

Breast cancer is one of the major causes of mortality in women worldwide. The most aggressive breast cancer subtypes are human epidermal growth factor receptor-positive (HER2+) and triple-negative breast cancers. Therapies targeting HER2 receptors have significantly improved HER2+ breast cancer patient outcomes. However, several recent studies have pointed out the deficiency of existing treatment protocols in combatting disease relapse and improving response rates to treatment. Overriding the inherent actions of the immune system to detect and annihilate cancer via the immune checkpoint pathways is one of the important hallmarks of cancer. Thus, restoration of these pathways by various means of immunomodulation has shown beneficial effects in the management of various types of cancers, including breast. We herein review the recent progress in the management of HER2+ breast cancer via HER2-targeted therapies, and its association with the programmed death receptor-1 (PD-1)/programmed death ligand-1 (PD-L1) axis. In order to link research in the areas of medicine and mathematics and point out specific opportunities for providing efficient theoretical analysis related to HER2+ breast cancer management, we also review mathematical models pertaining to the dynamics of HER2+ breast cancer and immune checkpoint inhibitors.

Molecular Profiling of the Metaplastic Spindle Cell Carcinoma of the Breast Reveals Potentially Targetable Biomarkers

INTRODUCTION

Spindle cell carcinoma is a rare subtype of metaplastic breast cancer, with triple-negative (TNBC: estrogen receptor-negative/progesterone receptor-negative/human epidermal growth factor receptor 2-negative) phenotype. It is associated with a marked resistance to conventional chemotherapy and has an overall poor outcome.

MATERIALS AND METHODS

Twenty-three pure spindle cell carcinomas of the breast (18 primary and 5 recurrent/metastatic) were comprehensively explored for biomarkers of immuno-oncology and targeted therapies using immunohistochemistry and DNA/RNA sequencing.

RESULTS

The majority (21/23) of spindle cell carcinomas were TNBC. Estrogen and androgen receptor expression above the therapeutic thresholds were detected in 2 cases each. Pathogenic gene mutations were identified in 21 of 23 cases, including PIK3CA, TP53, HRAS, NF1, and PTEN. One case with matched pre- and post-chemotherapy samples exhibited a consistent mutational profile (PIK3CA and HRAS mutations) in both samples. Gene amplifications were present in 5 cases, including 1 case without detectable mutations. The spindle cell carcinomas cohort had consistently low total mutational burden (all below the 80th percentile for the entire TNBC cohort). All tumors were microsatellite stable. Programmed death-ligand 1 expression was observed on both tumor cells (in 7/21 cases), and in tumor-infiltrating immune cells (2/21 cases).

CONCLUSIONS

Spindle cell carcinomas are characterized by targetable molecular alterations in the majority of cases, but owing to the lack of uniform findings, individual patient profiling is necessary. Detection of individual combinations of biomarkers should improve treatment options for this rare but aggressive disease.

Avoidance and Period-Shortening of Neoadjuvant Chemotherapy Against Triple-Negative Breast Cancer in Stages I and II: Importance of Ki-67 Labeling Index and the Recognition of Apocrine-Type Lesions

BACKGROUND

Triple-negative breast cancer encompasses heterogeneous subtypes. Neoadjuvant chemotherapy is ineffective against some triple-negative breast cancers, while others show a favorable prognosis despite chemoresistance.

METHODS

A total of 51 cases with stages I and II triple-negative breast cancer were analyzed; 34 triple-negative breast cancers treated with neoadjuvant chemotherapy were divided into "good responders" (n = 22), showing therapeutic effect G2b or G3 in surgical specimens, and "poor responders" with therapeutic effect G0, G1a, G1b, and G2a (n = 12). Neoadjuvant chemotherapy was spared in 17 cases (non-neoadjuvant chemotherapy group). Apocrine-type triple-negative breast cancer was defined as triple-negative breast cancer immunoreactive for both androgen receptor and forkhead-box protein A1. Triple-negative breast cancer other than apocrine-type (n = 16) and special types (myoepithelial, medullary, adenoid cystic, and spindle cell carcinomas, n = 6) was categorized as basal-like subtype (n = 29). Prognosis was evaluated in each category.

RESULTS

Neoadjuvant chemotherapy provoked significant effects against basal-like triple-negative breast cancer with high Ki-67 labeling (≧50%), and tumor-infiltrating lymphocytes predicted high chemosensitivity. Neoadjuvant chemotherapy was avoidable in triple-negative breast cancer of apocrine- and special types showing low (<50%) Ki-67 labeling. Ten (59%) lesions in the non-neoadjuvant chemotherapy group belonged to the apocrine-type. When clinical complete remission shown by contrast-enhanced magnetic resonance imaging was reached in the course of neoadjuvant chemotherapy against basal-like triple-negative breast cancer, the neoadjuvant chemotherapy period was shortened in 14 (64%) of 22 good responders. Disease-free and overall survival rates were excellent in all groups.

CONCLUSIONS

The following 2 hypothetical proposals should be proven by large-scale clinical trials. Immunohistochemical recognition of apocrine-type triple-negative breast cancer with low Ki-67 labeling is important for avoiding ineffective/unnecessary neoadjuvant chemotherapy. By employing appropriate clinical imaging, period-shortening is achievable in basal-like triple-negative breast cancer with high Ki-67 labeling.

PD-L1 status in breast cancer: Current view and perspectives

Breast cancer was traditionally not considered a particularly immunogenic tumor. However, recent developments have shown that some aggressive triple-negative breast cancers are immunogenic, exhibit a resistance to chemotherapy and have a poor prognosis. These cancers have been shown to express molecules identified as targets for immunotherapy. Despite the advances, the challenges are many, and include identifying the patients that may benefit from immunotherapy. The best methods to analyze these samples and to evaluate immunogenicity are also major challenges. Therefore, the most accurate and reliable assessment of immune cells as potential targets is one of the most important aims in the current research in breast immunotherapy. In the present review, we briefly discuss the mechanisms of the regulation of checkpoint inhibitors (PD-1/PD-L1) in breast cancer and explore the predictive aspects in the PD-L1 testing.

Prognosis in triple-negative apocrine carcinomas of the breast: A population-based study

BACKGROUND

Triple-negative apocrine carcinoma (TNAC) of the breast is a very rare type of breast cancer. Furthermore, the clinicopathological features, prognosis, and potential impact of treatment strategies in TNAC remain unclear.

METHODS

Data from the Surveillance, Epidemiology, and End Results (SEER) program were used to identify breast cancer patients diagnosed between 2010 and 2016 with TNAC and triple-negative breast cancer (TNBC, IDC [invasive ductal carcinoma], NOS [not otherwise specified]). Chi-squared tests were used to examine the categorical variables between the two groups. Overall survival (OS) of TNAC and TNBC was assessed by Kaplan-Meier analyses and Cox regression. Breast cancer-specific survival (BCSS) was evaluated by Nelson-Aalen analyses and competing risk regression.

RESULTS

We identified 31 362 patients from the SEER database, including 366 patients with TNAC and 30 996 patients with TNBC. TNAC was correlated with older age, lower T stage and lower tumor grade. Patients with TNAC had better OS compared with TNBC patients; the 5-year OS rates were 82.2% vs 73.5% (P < .001). The breast cancer-related death rate was significantly lower in patients with TNAC than in patients with TNBC, with a 5-year cumulative incidence of 9.1% vs 22.9% (P < .001). Chemotherapy was significantly associated with improved OS in TNAC patients, but radiotherapy was not associated with OS in TNAC patients. In the multivariable Cox regression, TNAC was still associated with improved OS (HR [hazard ratio], 0.61; 95% CI [confidence interval] 0.45-0.83; P = .002). In the multivariable competing risk regression, the significantly higher BCSS in patients with TNAC compared patients with TNBC remained (subdistribution HR [SHR], 0.42; 95% CI, 0.27-0.64; P < .001).

CONCLUSION

Patients with TNAC had a better prognosis than patients with TNBC, and chemotherapy was associated with survival advantages in TNAC patients.

Targeted immunotherapy with a checkpoint inhibitor in combination with chemotherapy: A new clinical paradigm in the treatment of triple-negative breast cancer

The treatment of several solid and hematologic malignancies with immune checkpoint inhibitors (against programmed death receptor-1/ligand-1 [PD-1/PD-L1]) has dramatically changed the cancer treatment paradigm. However, no checkpoint inhibitors were previously approved for the treatment of triple-negative breast cancer (TNBC), a difficult-to-treat disease with a high unmet therapeutic need. Based on IMpassion130 clinical trial (NCT02425891), the Food and Drug Administration (FDA) has recently granted an accelerated approval for atezolizumab (TECENTRIQ®), a monoclonal antibody drug targeting PD-L1, plus chemotherapy (Abraxane; nab®-Paclitaxel) for the treatment of adults with PD-L1-positive, unresectable, locally advanced or metastatic TNBC. The FDA has also approved the Ventana diagnostic antibody SP142 as a companion test for selecting TNBC patients for treatment with atezolizumab. In the present review, we briefly discuss the importance of this breakthrough as the first cancer immunotherapy regimen to be approved for the management of breast cancer.

Diagnostic impact of 18F-FDG PET/CT on the management of rare breast carcinomas: Apocrine and neuroendocrine carcinomas

OBJECTIVE

We aimed to evaluate the diagnostic impact of 18F-FDG PET/CT in staging apocrine breast carcinoma (ABC) and primary breast neuroendocrine carcinoma (PBNEC) and to demonstrate possible alterations of the 18F-FDG uptake in these histopathologic subtypes. In addition, we aimed to compare 18F-FDG PET/CT findings between ABC, PBNEC and invasive ductal carcinoma.

MATERIAL AND METHODS

A total of 570 patients and 585 breast lesions were retrospectively included in this study. After patients were classified into molecular subtypes according to the histopathological analysis, 18F-FDG PET/CT imaging was performed. The SUVmax findings of primary tumors obtained from 18F-FDG PET/CT were compared between the groups.

RESULTS

Invasive ductal carcinoma was the most prevalent breast carcinoma (77.7%, n=446), with a low proportion of ABC (4.1%, n=24) and PBNEC (2.4%; n=14) diagnosed. The highest mean SUVmax was calculated in HER2 subtype of ABC and 18F-FDG uptake ratio in HER2 and TN subtypes were found statistically higher than Luminal B type of ABC (p=0.038 and p=0.019, respectively). Although 18F-FDG uptake in Luminal B subtype of PBNEC was higher than Luminal A subtype, difference was not statistically significant. Additionally, the axillary metastasis rate was significantly higher in the ABC group (p=0.015).

CONCLUSIONS

The histopathological ABC subtype group showed different 18F-FDG uptake than the invasive ductal carcinoma group. Even if 18F-FDG uptake was lower in the PBNEC group than in the other groups, PET/CT showed and adequate performance in detecting primary tumors and metastases. The 18F-FDG PET/CT scan results may contribute to the initial staging and management of ABC and PBNEC patients.

Androgen receptor: A promising therapeutic target in breast cancer

Breast cancer (BCa) is the second most common cancer worldwide and the most prevalent cancer in women. The majority of BCa cases are positive (+) for the estrogen receptor (ER⁺, 80%) and progesterone receptor (PR⁺, 65%). Estrogen and progesterone hormones are known to be involved in cancer progression, and thus hormonal deprivation is used as an effective treatment for ER⁺PR⁺ BCa subtypes. However, some ER⁺PR⁺ BCa patients develop resistance to such therapies. Meanwhile, chemotherapy is the only available treatment for ER^-PR^- BCa tumors. Another hormone receptor known as the androgen receptor (AR) has also been found to be widely expressed in human breast carcinomas. However, the mechanisms of AR and its endogenous androgen ligands is not well-understood in BCa and its biological role in this hormone-related disease remains unclear. In this review, we aim to address the importance of the AR in BCa diagnosis and prognosis, current AR-targeting approaches in BCa, and the potential for AR-downstream molecules to serve as therapeutic targets.

Apocrine lesions of the breast: part 2 of a two-part review. Invasive apocrine carcinoma, the molecular apocrine signature and utility of immunohistochemistry in the diagnosis of apocrine lesions of the breast

Pure apocrine carcinoma of the breast is rare and has been defined by using a combination of morphologic (apocrine morphology in >90% of tumour cells) and immunohistochemical criteria (oestrogen receptor (ER) and progesterone receptor (PR) negative and androgen receptor (AR) positive). Recent advances in the molecular classification of breast tumours have uncovered a subset of breast tumours associated with high expression of androgen receptor mRNA including the so-called 'luminal androgen receptor (LAR) tumours' and 'molecular apocrine tumours' (MATs). Recognition of these tumour subsets has opened potential avenues for therapies exploiting the AR pathway in triple negative breast carcinoma (TNBC). In this second part of our two-part review, we focus on the definition of pure apocrine carcinoma, recent advances in understanding the molecular apocrine signature in breast carcinoma, its relationship to pure apocrine carcinoma defined at the level of light microscopy and immunohistochemistry (IHC) and the therapeutic implications of androgen expression in TNBC. We complete the article with a summary of the utility of IHC in stratifying apocrine lesions of the breast.

Triple Negative Apocrine Carcinomas as a Distinct Subtype of Triple Negative Breast Cancer: A Case-control Study

BACKGROUND

Invasive triple negative apocrine carcinoma (TNAC) of the breast is a rare type of triple negative breast cancer. Several studies reported significantly distinct prognosis for TNAC when compared with most of the non-apocrine triple negative (NATN) tumors. This is a case-control study reporting onoutcomes from our long-term single-center experience.

PATIENTS AND METHODS

We analyzed the clinicopathologic features of a series of 46 TNAC tumors treated in a 15-year period. Tumor characteristics and outcomes have been compared with a homogeneous control series of 43 NATN tumors treated during the same follow-up period. Local relapse-free survival (LRFS), distant metastases-free survival (DMFS), and overall survival (OS) have been evaluated.

RESULTS

LRFS in the TNAC group was 85% and 78% at 5 and 10 years, respectively. LRFS in the NATN group was 90% and 79% at 5 and 10 years, respectively (hazard ratio [HR], 1.14; 95% confidence interval [CI], 0.41-3.19; P = .80). DMFS in the TNAC group was 85% and 85% at 5 and 10 years, respectively. DMFS in the NATN group was 85% and 75% at 5 and 10 years, respectively (HR, 0.39; 95% CI, 0.14-1.08; P = .071). OS in the TNAC group was 86% and 83% at 5 and 10 years, respectively. OS in the NATN group was 86% and 63% at 5 and 10 years, respectively. OS was significantly better in the TNAC group (HR, 0.45; 95% CI, 0.20-0.99; P = .049).

CONCLUSIONS

TNAC seems to represent a distinct group of triple negative breast cancer, characterized by a favorable long-term outcome when compared with NATN tumors.