Mammary Epithelial-Myoepithelial Carcinoma: Report of a Case With HRAS and PIK3CA Mutations by Next-Generation Sequencing

Epithelial-myoepithelial carcinoma occurrence in the site of previously treated ductal carcinoma in situ of the breast: Imaging features with histopathologic correlation, a case report and review of the literature

Key Clinical Message

Epithelial-myoepithelial carcinoma of the breast is an extremely rare biphasic tumor. This report documents the first case of epithelial-myoepithelial carcinoma presenting in the location of a previously treated ductal carcinoma in order to increase the awareness of this entity as a potential differential for recurrent breast lesions.

Abstract

Epithelial-myoepithelial carcinoma of the breast is an exceedingly rare biphasic tumor, seldom documented in medical literature. This report describes the first known case of this entity at the site of a previously treated neoplasm in a 75-year-old female with a history of high-grade ductal carcinoma in situ who presented with a new breast mass. Imaging demonstrated an oval shaped mass with microlobulated borders and hypoechoic echogenicity on ultrasound. Following multidisciplinary discussion, she underwent a mastectomy, revealing epithelial-myoepithelial carcinoma with metaplastic squamous cell carcinoma. The patient began chemotherapy but discontinued due to poor tolerance and neurological complications. Generally, prognosis for epithelial-myoepithelial carcinoma (World Health Organization Classification of Breast Tumors 2019, 8562/3) is highly variable, with limited available data suggesting that epithelial-myoepithelial carcinoma may follow a course similar to that of breast adenocarcinomas with both hematogenous and lymphatic spread. Treatment typically involves curative excision, though the role of axillary lymph node sampling remains under discussion. This case underscores the need for vigilance in post-treatment surveillance for breast cancer and highlights the importance of recognizing this entity in recurrent breast pathology.

Invasive Carcinoma With Skin Adnexal Trichilemmal Hair Follicular Differentiation Occurring in the Breast: A Case Report With Detailed Immunohistochemical and Molecular Analysis

Cutaneous-type adnexal tumors involving the breast are rare and create a diagnostic dilemma as they are often indistinguishable from primary mammary neoplasms. Tumors showing hair follicular differentiation are particularly challenging due to their rarity and the subtle appreciation of the intricate microanatomy of the hair follicle. We report a triple negative cutaneous-type adnexal carcinoma with follicular differentiation involving the breast to bring attention to the existence of these specialized group of tumors which should be managed differently from conventional triple negative carcinomas of the breast.

Translational Aspects in Metaplastic Breast Carcinoma

Breast cancer is the most common cancer among women. Metaplastic breast carcinoma (MpBC) is a rare, heterogeneous group of invasive breast carcinomas, which are classified as predominantly triple-negative breast carcinomas (TNBCs; HR-negative/HER2-negative). Histologically, MpBC is classified into six subtypes. Two of these are considered low-grade and the others are high-grade. MpBCs seem to be more aggressive, less responsive to neoadjuvant chemotherapy, and have higher rates of chemoresistance than other TNBCs. MpBCs have a lower survival rate than expected for TNBCs. MpBC treatment represents a challenge, leading to a thorough exploration of the tumor immune microenvironment, which has recently opened the possibility of new therapeutic strategies. The epithelial-mesenchymal transition in MpBC is characterized by the loss of intercellular adhesion, downregulation of epithelial markers, underexpression of genes with biological epithelial functions, upregulation of mesenchymal markers, overexpression of genes with biological mesenchymal functions, acquisition of fibroblast-like (spindle) morphology, cytoskeleton reorganization, increased motility, invasiveness, and metastatic capabilities. This article reviews and summarizes the current knowledge and translational aspects of MpBC.

Salivary Gland-like Tumors of the Breast

CONTEXT

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

OBJECTIVE

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

DATA SOURCES

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

CONCLUSIONS

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

Metaplastic Carcinoma of the Breast: Case Series of a Single Institute and Review of the Literature

Metaplastic carcinoma of the breast (MpBC) is a very rare and aggressive type of breast cancer. Data focusing on MpBC are limited. The aim of this study was to describe the clinicopathological features of MpBC and evaluate the prognosis of patients with MpBC. Eligible articles about MpBC were identified by searching CASES SERIES gov and the MEDLINE bibliographic database for the period of 1 January 2010 to 1 June 2021 with the keywords metaplastic breast cancer, mammary gland cancer, neoplasm, tumor, and metaplastic carcinoma. In this study, we also report 46 cases of MpBC stemming from our hospital. Survival rates, clinical behavior, and pathological characteristics were analyzed. Data from 205 patients were included for analysis. The mean age at diagnosis was 55 (14.7) years. The TNM stage at diagnosis was mostly stage II (58.5%) and most tumors were triple negative. The median overall survival was 66 (12-118) months, and the median disease-free survival was 56.8 (11-102) months. Multivariate Cox regression analysis revealed that surgical treatment was associated with decreased risk of death (hazard ratio 0.11, 95% confidence interval 0.02-0.54, p = 0.01) while advanced TNM stage was associated with increased risk of death (hazard ratio 1.5, 95% confidence interval 1.04-2.28, p = 0.03). Our results revealed that surgical treatment and TNM stage were the only independent risk factors related to patients' overall survival.

Breast lesions with myoepithelial phenotype

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

Epithelial-myoepithelial carcinoma of the nasopharynx: A case report and review of the literature

Background

Epithelial-myoepithelial carcinoma (EMCa) is a rare low-grade malignant tumor that most commonly occurs in the salivary glands, with approximately 320 cases having been reported worldwide. Here, we report the third case of EMCa occurring in the nasopharynx. Rare cases in the breast, pituitary gland, lacrimal gland, nose, paranasal sinus, nasal cavity, trachea and bronchus, lung, and even the pleura mediastinalis have also been reported. Histopathology and immunohistochemistry are useful for confirming the diagnosis of EMCa, which is characterized by biphasic tubular structures composed of inner ductal and outer clear myoepithelial cells and stains for different markers in each layer. However, because of the rarity of EMCa, the clinicopathological characteristics and treatment of these patients remain unclear.

Case presentation

We report a rare case of EMCa of the nasopharynx. A 51-year-old man presented with a 5-month history of pain while swallowing and aggravation accompanied by right ear tinnitus lasting for 1 month. Nasopharyngoscopy and magnetic resonance imaging (MRI) of the nasopharynx and neck revealed a 5.6 cm × 3.4 cm × 3.1 cm mass in the nasopharyngeal space, invasion of the right cavernous sinus, and lymph node enlargement in the right retropharyngeal space. On 17 April 2019, based on the histopathological and immunohistochemical features, a final diagnosis of EMCa of the right nasopharynx was made. The patient underwent concurrent chemoradiotherapy (CCRT), and his symptoms were relieved after treatment. On 10 January 2022, nasopharynx MRI and biopsy revealed local recurrence, but chest and abdominal computed tomography (CT) showed no obvious signs of metastasis. The local recurrence-free survival (LRFS) period was 33 months.

Conclusion

To the best of our knowledge, this is the third reported case of EMCa in the nasopharynx and the only case of EMCa in the nasopharynx treated with CCRT, and a partial response was achieved. Therefore, to improve the quality of life and prognosis of patients with unresectable tumors, we believe that CCRT is a suitable option. Further clinical observations are required to elucidate the pathophysiology and prognosis of EMCa.

Pulmonary epithelial-myoepithelial carcinoma (P-EMC) with focal high grade transformation: Molecular and cytologic findings

BACKGROUND

Pulmonary epithelial-myoepithelial carcinoma (P-EMC) is a rare type of salivary gland tumor of the lung. Diagnosis from preoperative biopsies or fine needle aspiration (FNA) cytology specimens is difficult given the rarity of the tumor and overlapping cytomorphology with other entities. These tumors generally have a good prognosis, however prior reports of recurrence and metastasis to lymph nodes have been reported. Further, little is known about the malignant potential of high grade transformation. The molecular characteristics of this entity are unknown, with only a few case reports commenting on molecular findings. Here, we report a case of P-EMC with focal high grade transformation. We present its diagnostic pitfalls on cytology specimens, surgical pathology, immunohistochemistry, and molecular findings.

CASE PRESENTATION

A 72 year old female presented with an incidentally detected lung mass. A chest computed tomography (CT) demonstrated a left hilar mass measuring 4.1 cm with endobronchial extension into the left upper lobe. On the initial endobronchial core needle biopsy and cytology FNA, the tumor was misinterpreted as squamous cell carcinoma. The patient subsequently underwent a left pneumonectomy along with mediastinal lymph node dissection. Final surgical pathology of the resection specimen indicated a P-EMC with focal high grade transformation. The patient is disease-free 1 year post-surgery.

CONCLUSIONS

Due to the rarity of P-EMC, insufficient sampling and histologic heterogeneity, diagnosis of P-EMC on preoperative core needle biopsy or FNA specimen is difficult. Herein, we present a rare case of P-EMC, with a pre-operative FNA cytology specimen that consisted of tumor cells with dense cytoplasm and moderate cytologic atypia, strong positive staining pattern of p40, that was misdiagnosed as squamous cell carcinoma. Follow up surgical resection showed P-EMC with focal high grade transformation. Salivary gland EMCs with high grade transformation have previously been reported to have a worse prognosis, however, little is known about the malignant potential in the lung. Next generation sequencing (NGS) using a 397-gene solid tumor panel identified variants in DNMT3A, APC, STAT3 in both low and high grade components, while KDM5C was present only in the high grade transformation.

Malignant adenomyoepithelioma of the breast: Two case reports and review of the literature

BACKGROUND

Malignant adenomyoepithelioma (AME) of the breast is a rare tumor in which malignancy can arise from either epithelial or myoepithelial components, or from both cell types. The incidence and prognosis of malignant AME of the breast are difficult to assess due to its rarity. Therefore, the optimal treatment for this disease is still controversial.

CASE SUMMARY

We present two middle-aged women (48 and 56 years old) with malignant AME of the breast. Core needle biopsy was performed before surgery. However, breast adenoma and malignant tumors were observed. The preoperative diagnosis of malignant AME of the breast is still challenging for pathologists and clinicians. Both patients underwent mastectomy and sentinel lymph node biopsy, both of which were negative, followed by adjuvant chemotherapy.

CONCLUSION

The follow-up duration of the two patients was two years and four months, respectively. No signs of relapse or metastasis have been observed thus far.

Triple-negative breast carcinomas of low malignant potential: review on diagnostic criteria and differential diagnoses

Triple-negative breast carcinomas constitute a wide spectrum of lesions, mostly being highly aggressive. Nevertheless, some special histologic subtypes can have low malignant potential. The purpose of the present paper is to review diagnostic criteria and prognostic parameters of breast neoplasms of special histotypes. Specifically, adenoid cystic carcinoma, adenomyoepithelioma, acinic cell carcinoma, mucoepidermoid carcinoma, tall cell carcinoma with reverse polarity, and secretory carcinoma will be discussed. For each tumour, definition and morphological and molecular features, together with prognostic parameters, will be presented. Paradigmatic cases will be illustrated.

Hormonal Receptors, Human Epidermal Growth Factor Receptor-2 and Triple Negative Immunohistochemical Typing in Women with Breast Cancer in Kampala, Uganda

Background

The expression of estrogen and progesterone receptors (ER and PR) and human epidermal growth factor receptor-2 (HER2) has been reported to have an invaluable prognostic role. The aim of this study was to determine the expression of ER, PR and HER2 in women with breast cancer (BC) in Kampala, Uganda.

Methods

Expression of ER, PR and HER2 was determined immunohistochemically. Logistic regression was performed to determine the effect of the independent factors in predicting the risk of not expressing the breast markers. A two-tailed p<0.05 was regarded to be statistically significant.

Results

ER, PR and HER2 were expressed in 53.4%, 46.6% and 18.5%, respectively. ER and PR co-expression was present in 42.7% and 37.9% patients had triple negative breast cancer (TNBC). Age was an independent predictor of expression of ER (AOR = 0.18, 95% CI = 0.062–0.541, p = 0.002) and PR (AOR = 0.35, 95% CI = 0.129–0.968, p = 0.043).

Conclusion

The majority of patients in this study had less than 50 years with high tumour grade. Interestingly, most of them had high expression of HER2 with TNBC which are molecular subtypes of BC with poor prognosis. Age was an independent predictor of expression of both ER and PR.

Epithelial-Myoepithelial Carcinoma of the Breast with Rhabdoid Features

Epithelial-myoepithelial carcinoma of the breast is a rare biphasic tumor composed of intermixed malignant epithelial and myoepithelial components. Myoepithelial cells are known to adopt varied morphologies, including spindle, chondroid, clear cell, and rhabdoid morphologies, and can represent a diagnostic challenge when isolated on biopsy. Rhabdomyosarcoma, phyllodes tumor, metaplastic carcinoma, and myoepithelial carcinoma are primary breast tumors that all have been shown to exhibit rhabdoid features, whether representing true differentiation or morphological mimic. We here report an epithelial-myoepithelial carcinoma of the breast with rhabdoid features in a 76-year-old woman. The rhabdoid-appearing myoepithelial cells are negative for myogenin, consistent with a rhabdoid-like morphology rather than a true rhabdoid differentiation, comparably to previously described myoepithelial carcinoma with rhabdoid features. To our knowledge, this is the first reported case of epithelial-myoepithelial carcinoma of the breast with rhabdoid features and thus adds another entity to the differential diagnosis of breast lesions with rhabdoid features.

Molecular Features of Metaplastic Breast Carcinoma: An Infrequent Subtype of Triple Negative Breast Carcinoma

Metaplastic breast carcinoma (MBC) is a heterogeneous group of infrequent invasive carcinomas that display differentiation of the neoplastic epithelium towards squamous cells and/or mesenchymal-type elements. Most MBC have a triple negative phenotype and poor prognosis. Thus, MBC have worse survival rates than other invasive breast carcinomas, including other triple negative breast carcinomas (TNBC). In this study, we reviewed the molecular features of MBC, pointing out the differences among subtypes. The most frequently mutated genes in MBC were TP53 and PIK3CA. Additionally, mutations in the other genes of the PI3K/AKT pathway indicated its importance in the pathogenesis of MBC. Regarding copy number variations (CNVs), MYC was the most frequently amplified gene, and the most frequent gene loss affected the CDKN2A/CDKN2B locus. Furthermore, the pattern of mutations and CNVs of MBC differed from those reported in other TNBC. However, the molecular profile of MBC was not homogeneous among histological subtypes, being the alterations in the PI3K pathway most frequent in spindle cell carcinomas. Transcriptomic studies have demonstrated an epithelial to mesenchymal program activation and the enrichment of stemness genes in most MBC. In addition, current studies are attempting to define the immune microenvironment of these tumors. In conclusion, due to specific molecular features, MBC have a different clinical behavior from other types of TNBC, being more resistant to standard chemotherapy. For this reason, new therapeutic approaches based on tumor molecular characteristics are needed to treat MBC.

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.

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.

Understanding the histogenesis of a HRAS-PIK3R1 co-driven metastatic metaplastic breast carcinoma associated with squamous metaplasia of lactiferous ducts

Metaplastic breast carcinoma (MBC) represents a heterogeneous group of aggressive primary breast cancers that can show differentiation into carcinomatous and sarcomatous elements. Due to its rapid growth, this malignancy can replace precursor lesions, which remain unknown in most cases. Herein, we describe a MBC presenting as a deceptive post-biopsy hematoma. Histopathological and immunohistochemical evaluation of the primary tumor revealed a squamous cell carcinoma arising in a background of squamous metaplasia of lactiferous ducts (SMOLD). In the absence of ductal carcinoma in situ, we consider SMOLD as a nonobligatory precursor of MBC. The tumor showed 'dedifferentiation' into spindle, mucin-producing, osteoclast-like giant cell and fibromatosis-like carcinoma. Next-generation sequencing revealed the driver mutations HRAS^Q61R and PIK3R1^{c.1738_1745+2del} in addition to MYH11^S638L and amplification of ERCC5 and FGF14, which were potential contributors to tumor phenotype. Tumor dedifferentiation was probably facilitated by epithelial-to-mesenchymal transition (EMT) with aberrant expression of platelet and endothelial adhesion molecule-1, leading to early metastasis via hematogenous route rather than lymphatic. The co-occurrence of phosphoinositide 3-kinase and mitogen-activated protein kinase pathway abnormalities along with EMT could mediate divergent growth in breast cancer.

Malignant transformation in a Breast Adenomyoepithelioma Caused by Amplification of c-MYC: A Common pathway to Cancer in a Rare Entity

Breast adenomyoepitheliomas are composed of a biphasic proliferation of myoepithelial cells around small epithelial-lined spaces. Due to the rarity of adenomyoepitheliomas, the molecular data describing them are limited. Adenomyoepitheliomas are considered to be benign or have low malignant potential, and be prone to local recurrence. Malignant transformation has been associated with homozygous deletion of CDKN2A or somatic mutations in TERT, but remains unexplained in many cases. Here, we describe a case of carcinomatous transformation of both epithelial and myoepithelial cells in an estrogen receptor-negative adenomyoepithelioma caused by amplification of MYC. Break-apart fluorescence in situ hybridization revealed an increase in the MYC gene copy number (3–4 copies/cell in 37%, > 4 copies/cell in 40%). Deregulation of MYC is responsible for uncontrolled proliferation and cellular immortalization in basal-like breast cancers. Our case demonstrates that genomic instability events associated with gene amplification may be involved in the carcinogenesis of malignant adenomyoepitheliomas.