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Webersinke G, Burghofer J, Malli T, Rammer M, Jahn SW, Niendorf A, Tavassoli FA, Moinfar F. TERT Promoter Mutation c.-124C>T Commonly Occurs in Low-Grade Fibromatosis-like Metaplastic Breast Carcinoma. Arch Pathol Lab Med 2023; 147:1451-1457. [PMID: 36897999 DOI: 10.5858/arpa.2022-0159-oa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/28/2022] [Indexed: 03/12/2023]
Abstract
CONTEXT.— Low-grade fibromatosis-like metaplastic carcinoma (FLMC) is a very rare subtype of triple-negative metaplastic (spindle cell) breast carcinoma. It is characterized by the proliferation of spindle cells closely resembling fibromatosis, which represents a benign fibroblastic/myofibroblastic breast proliferation. Unlike most triple-negative and basal-like breast cancers, FLMC has a very low potential for metastases, but demonstrates frequent local recurrences. OBJECTIVE.— To genetically characterize FLMC. DESIGN.— To this end, we analyzed 7 cases by targeted next-generation sequencing for 315 cancer-related genes and performed comparative microarray copy number analysis in 5 of these cases. RESULTS.— All cases shared TERT alterations (6 patients with recurrent c.-124C>T TERT promoter mutation and 1 patient with copy number gain encompassing the TERT locus), had oncogenic PIK3CA/PIK3R1 mutations (activation of the PI3K/AKT/mTOR pathway), and lacked mutations in TP53. TERT was overexpressed in all FLMCs. CDKN2A/B loss or mutation was observed in 4 of 7 cases (57%). Furthermore, tumors displayed chromosomal stability, with only few copy number variations and a low tumor mutational burden. CONCLUSIONS— We conclude that FLMCs typically show the recurrent TERT promoter mutation c.-124C>T, activation of the PI3K/AKT/mTOR pathway, low genomic instability, and wild-type TP53. In conjunction with previous data of metaplastic (spindle cell) carcinoma with and without fibromatosis-like morphology, FLMC is most likely distinguished by TERT promoter mutation. Thus, our data support the notion of a distinct subgroup within low-grade metaplastic breast cancer with spindle cell morphology and associated TERT mutations.
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Affiliation(s)
- Gerald Webersinke
- From the Laboratory for Molecular Genetic Diagnostics, Ordensklinikum Linz/Hospital of the Sisters of Charity, Linz, Austria (Webersinke, Burghofer, Malli, Rammer)
| | - Jonathan Burghofer
- From the Laboratory for Molecular Genetic Diagnostics, Ordensklinikum Linz/Hospital of the Sisters of Charity, Linz, Austria (Webersinke, Burghofer, Malli, Rammer)
| | - Theodora Malli
- From the Laboratory for Molecular Genetic Diagnostics, Ordensklinikum Linz/Hospital of the Sisters of Charity, Linz, Austria (Webersinke, Burghofer, Malli, Rammer)
| | - Melanie Rammer
- From the Laboratory for Molecular Genetic Diagnostics, Ordensklinikum Linz/Hospital of the Sisters of Charity, Linz, Austria (Webersinke, Burghofer, Malli, Rammer)
| | - Stephan Wenzel Jahn
- Diagnostic and Research Institute of Pathology, Medical University of Graz, Graz, Austria (Jahn, Moinfar)
| | - Axel Niendorf
- Department of Pathology and Molecular Diagnostic, Hamburg-West, Hamburg, Germany (Niendorf)
| | - Fattaneh A Tavassoli
- Department of Pathology, Yale University School of Medicine, New Haven Connecticut (Tavassoli)
| | - Farid Moinfar
- Diagnostic and Research Institute of Pathology, Medical University of Graz, Graz, Austria (Jahn, Moinfar)
- Department of Pathology and Molecular Pathology, Vinzenz Pathologieverbund Linz, Austria (Moinfar)
- The Vincent Academy of Pathology, Linz, Austria (Moinfar)
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Ito R, Ota D, Ando S, Mori M, Fukuuchi A. A case of adenomyoepithelioma with myoepithelial carcinoma of the breast. Clin Case Rep 2019; 7:930-934. [PMID: 31110717 PMCID: PMC6509899 DOI: 10.1002/ccr3.2100] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/15/2019] [Accepted: 02/22/2019] [Indexed: 12/27/2022] Open
Abstract
Adenomyoepithelioma with myoepithelial carcinoma of the breast is rare and diagnosed with histology and immunohistochemistry. We present a case of malignant transformation over 10 years, with ultrasonographic findings, highlighting the importance of an early excisional biopsy. Conservative surgery and radiation therapy were performed. There was no recurrence for 2 years.
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Affiliation(s)
- Ryota Ito
- Department of Breast and Endocrine SurgeryMitsui Memorial HospitalTokyoJapan
| | - Daisuke Ota
- Department of Breast and Endocrine SurgeryMitsui Memorial HospitalTokyoJapan
| | - Sumiyo Ando
- Department of Diagnostic PathologyMitsui Memorial HospitalTokyoJapan
| | - Masaya Mori
- Department of Diagnostic PathologyMitsui Memorial HospitalTokyoJapan
| | - Atsushi Fukuuchi
- Department of Breast and Endocrine SurgeryMitsui Memorial HospitalTokyoJapan
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Janostiak R, Vyas M, Cicek AF, Wajapeyee N, Harigopal M. Loss of c-KIT expression in breast cancer correlates with malignant transformation of breast epithelium and is mediated by KIT gene promoter DNA hypermethylation. Exp Mol Pathol 2018; 105:41-49. [PMID: 29852185 DOI: 10.1016/j.yexmp.2018.05.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 05/26/2018] [Indexed: 12/21/2022]
Abstract
KIT Proto-Oncogene Receptor Tyrosine Kinase (KIT) is a transmembrane receptor tyrosine kinase which plays an important role in regulation of cell proliferation, survival and migration. Interestingly, the role of c-KIT in malignant transformation seems to be highly tissue-specific and it can act either as an oncogene or tumor suppressor gene. Here we analyzed the expression of c-KIT in normal breast tissues and tissues from different stages encompassing major steps of breast tumor development. Our study showed, that the c-KIT protein expression is gradually lost during the process of breast tissue transformation. The analysis of previously published datasets revealed that c-KIT expression in breast malignancies was downregulated at mRNA level. Because sequencing studies did not identify any recurrent mutations or copy number alterations, we proposed a potential epigenetic mechanism for the downregulation of c-KIT expression. In-silico analysis of the KIT promoter revealed the presence of CpG islands, therefore we performed bisulfite sequencing of normal breast epithelial tissues as well as breast tumor samples. We found, that KIT promoter is hypermethylated in breast tumors compared to normal breast tissues. Furthermore, treatment of breast cancer cell lines, that lack the expression of c-KIT, with methyltransferase inhibitor 5-Azacytidine (5Aza-2dC) resulted in increased expression of c-KIT mRNA. Collectively, our studies demonstrate that c-KIT expression is epigenetically downregulated during breast epithelium transformation and cancer development via KIT promoter hypermethylation.
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Affiliation(s)
- Radoslav Janostiak
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06510, USA.
| | - Monika Vyas
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Ali Fuat Cicek
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Narendra Wajapeyee
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Malini Harigopal
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06510, USA
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Cheah AL, Billings SD, Rowe JJ. Mesenchymal tumours of the breast and their mimics: a review with approach to diagnosis. Pathology 2016; 48:406-24. [DOI: 10.1016/j.pathol.2016.05.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 05/20/2016] [Accepted: 05/23/2016] [Indexed: 12/16/2022]
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5
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Sánchez-Céspedes R, Millán Y, Guil-Luna S, Reymundo C, Espinosa de Los Monteros A, Martín de Las Mulas J. Myoepithelial cells in canine mammary tumours. Vet J 2015; 207:45-52. [PMID: 26639832 DOI: 10.1016/j.tvjl.2015.10.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 10/07/2015] [Accepted: 10/10/2015] [Indexed: 02/05/2023]
Abstract
Mammary tumours are the most common neoplasms of female dogs. Compared to mammary tumours of humans and cats, myoepithelial (ME) cell involvement is common in canine mammary tumours (CMT) of any subtype. Since ME cell involvement in CMT influences both histogenetic tumour classification and prognosis, correct identification of ME cells is important. This review describes immunohistochemical methods for identification of canine mammary ME cells used in vivo. In addition, phenotypic and genotypic methods to isolate ME cells for in vitro studies to analyse tumour-suppressor protein production and gene expression are discussed. The contribution of ME cells to both histogenetic classifications and the prognosis of CMT is compared with other species and the potential use of ME cells as a method to identify carcinoma in situ is discussed.
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Affiliation(s)
| | - Yolanda Millán
- Department of Comparative Pathology, University of Córdoba, 14014 Córdoba, Spain
| | - Silvia Guil-Luna
- Department of Comparative Pathology, University of Córdoba, 14014 Córdoba, Spain
| | - Carlos Reymundo
- Department of Pathology, University of Córdoba, 14071 Córdoba, Spain
| | - Antonio Espinosa de Los Monteros
- Unit of Histology and Animal Pathology, Institute for Animal Health, Veterinary School, University of Las Palmas de Gran Canaria, 35413 Las Palmas, Spain
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6
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Kővári B, Báthori Á, Cserni G. CD10 Immunohistochemical Expression in Apocrine Lesions of the Breast. Pathobiology 2015; 82:259-63. [PMID: 26562027 DOI: 10.1159/000440664] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 08/24/2015] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE In the breast, CD10 is expressed by myoepithelial cells (MECs), and apocrine metaplasia has also been mentioned as being positive with this marker. Apocrine lesions have been explored for the expression of CD10. METHODS The apocrine lesions studied included 11 cysts, 6 cases of apocrine adenosis, 2 of apocrine metaplasia or hyperplasia in papilloma, 13 ductal carcinomas in situ (DCIS) and invasive carcinomas (14 ductal and 4 lobular). RESULTS Benign apocrine lesions showed complete or partial luminal CD10 staining, although most cases included parts without staining, and 2 lesions were completely negative. The MECs were often but not always positive. Nine of the 13 cases of apocrine DCIS displayed no luminal staining, but 4 demonstrated very focal luminal positivity. The MECs around the DCIS showed a spectrum of staining from nil to strong and complete. Only 4 invasive carcinomas demonstrated luminal/membranous staining. Cytoplasmic CD10 positivity was seen focally in 4 invasive cancers and in 3 DCIS. CONCLUSION CD10 positivity is luminal/membranous in most benign apocrine lesions, the staining being nonuniversal and sometimes focal. Analogous staining in apocrine malignancies seems rarer in DCIS and even rarer in invasive apocrine carcinomas, but atypical cytoplasmic positivity may also occur. CD10 is not an ideal myoepithelial marker in apocrine lesions.
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Affiliation(s)
- Bence Kővári
- Department of Pathology, University of Szeged, Szeged, Hungary
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7
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Ingthorsson S, Hilmarsdottir B, Kricker J, Magnusson MK, Gudjonsson T. Context-Dependent Function of Myoepithelial Cells in Breast Morphogenesis and Neoplasia. CURRENT MOLECULAR BIOLOGY REPORTS 2015; 1:168-174. [PMID: 28680803 PMCID: PMC5487766 DOI: 10.1007/s40610-015-0027-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Myoepithelial cells (MEPs) are specialized cells derived from epithelial progenitor cells, yet they also express the contractile machinery of smooth muscle cells. MEPs are prominent in glandular tissues where their function is to help expel secretions generated by the glandular epithelial cells. In the breast, MEPs are part of the bi-layered breast epithelium that line ducts and alveoli positioned perpendicular to the luminal epithelial cells (LEPs), separated from the surrounding stroma by the basement membrane. Researchers have recognized MEPs as important regulators of structural and functional behavior of LEPs, namely having role in polarization of LEPs, and regulating milk production. Furthermore, they have also been proposed to act as tumor suppressors as their presence inhibits invasion of cancer cells into the surrounding stroma. There is, however, accumulating evidence that MEPs in normal breast, carcinoma in situ and in invasive breast cancer differ significantly in terms of marker expression and this may truly interfere with their ability to behave as tumor suppressors. The term myoepithelial cell is often used synonymously with basal cell. While all MEPs, due to their position, can be referred to as basal cells, some basal cells do not fulfill the criteria of being MEPs. Synonymous use of these terms may hold true under normal conditions but careful interpretation of these terms should be used in breast cancer. In recent years, partial myoepithelial differentiation and epithelial to mesenchymal transition (EMT) have been shown to be associated with, and in some cases, necessary for cancer invasion and metastasis. In this review, we will discuss the context-dependent role of MEPs in breast morphogenesis, tumor suppression, and also the appearance of basal or partial myoepithelial differentiation in aggressive forms of breast cancer.
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Affiliation(s)
- Saevar Ingthorsson
- Stem Cell Research Unit, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Laboratory Hematology, Landspítali-University Hospital, Reykjavik, Iceland
| | - Bylgja Hilmarsdottir
- Stem Cell Research Unit, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Laboratory Hematology, Landspítali-University Hospital, Reykjavik, Iceland
| | - Jennifer Kricker
- Stem Cell Research Unit, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Laboratory Hematology, Landspítali-University Hospital, Reykjavik, Iceland
| | - Magnus Karl Magnusson
- Stem Cell Research Unit, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Laboratory Hematology, Landspítali-University Hospital, Reykjavik, Iceland
| | - Thorarinn Gudjonsson
- Stem Cell Research Unit, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Laboratory Hematology, Landspítali-University Hospital, Reykjavik, Iceland
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Abstract
Metaplastic carcinoma of the breast is a rare but aggressive type of breast cancer that has been recognized as a unique pathologic entity by the World Health Organization. Morphologically, it is characterized by the differentiation of neoplastic epithelium into squamous cells and/or mesenchymal-looking elements (squamous cells, spindle cells, cartilage or bone, etc). It shares many similarities with invasive ductal carcinoma and benign lesions on mammography, which further complicates the diagnosis. Treatment for metaplastic breast carcinoma is relatively unknown because of the rarity of the disease, but studies suggest that removal of the tumor and adjuvant radiation therapy has the greatest benefit.
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Affiliation(s)
- Elizabeth McKinnon
- From the Department of Pathology, The Brooklyn Hospital Center/NewYork-Presbyterian Healthcare System, Brooklyn, New York. Dr McKinnon is currently located at the Department of Pathology, Duke University Medical Center, Durham, North Carolina
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9
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Safarpour D, Tavassoli FA. A targetable androgen receptor-positive breast cancer subtype hidden among the triple-negative cancers. Arch Pathol Lab Med 2014; 139:612-7. [PMID: 25310144 DOI: 10.5858/arpa.2014-0122-ra] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
CONTEXT Triple-negative breast cancer (TNBC) is a subgroup of breast cancers that by definition lack expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2). A diverse group of tumors, TNBC shares some morphologic and molecular features with basal-like breast cancer, a category of breast cancer defined by gene expression profiling. More likely to occur in young women and African Americans, TNBCs may exhibit aggressive behavior and are associated with poor prognosis despite their initial response to conventional chemotherapy. Because hormonal or HER2-targeted therapies are ineffective for these tumors, the main therapeutic option is systemic chemotherapy. Therefore, identification of new targets for therapy is urgently needed for this group. OBJECTIVE To review and present recent literature along with our own experience regarding the clinical and morphologic characteristics and the prevalence of androgen receptor (AR) expression in TNBC, and to discuss the potential use of AR as a therapeutic target for AR(+) TNBC. DATA SOURCES Data sources are published articles from peer-reviewed journals in PubMed (US National Library of Medicine). CONCLUSIONS AR is the most commonly expressed hormone receptor among all breast carcinomas, with a prevalence of 25% to 75% among TNBCs. Therefore, we strongly support the routine assessment of AR in TNBC, and preferably in all breast carcinomas.
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Affiliation(s)
- Damoun Safarpour
- From the Department of Pathology, Yale University School of Medicine, New Haven, Connecticut
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10
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Tan PH, Ellis IO. Myoepithelial and epithelial-myoepithelial, mesenchymal and fibroepithelial breast lesions: updates from the WHO Classification of Tumours of the Breast 2012. J Clin Pathol 2013; 66:465-70. [PMID: 23533258 DOI: 10.1136/jclinpath-2012-201078] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In the 4th edition of the WHO Classification of Tumours of the Breast, myoepithelial lesions are retitled myoepithelial and epithelial-myoepithelial lesions in order to better reflect the dual participation of luminal and myoepithelial compartments in some key entities. Malignant myoepithelioma, described as a section within the chapter on myoepithelial lesions in the 3rd edition, is recognised in the 4th edition as part of metaplastic carcinoma. Adenomyoepithelioma with malignancy is categorised in terms of the cellular component undergoing malignant transformation. The list of antibodies that can be used for identifying myoepithelial cells is updated. Among mesenchymal lesions, new additions are nodular fasciitis and atypical vascular lesions, while the haemangiopericytoma is removed. The 3rd edition stated that pathological prediction of behaviour of phyllodes tumours is difficult in the individual case. In the 4th edition, some progress has been made in prioritisation and weighting of histological parameters that can potentially estimate probability of recurrence. The WHO Working Group advocates leaning towards a diagnosis of fibroadenoma in cases where there is histological uncertainty in distinction from a benign phyllodes tumour, or adopting the neutral term 'benign fibroepithelial neoplasm', as the clinical behaviour of fibroadenoma overlaps with that of benign phyllodes tumour. The 3rd edition terminology of 'periductal stromal sarcoma' is revised to 'periductal stromal tumour', akin to the widespread consensus to avoid the use of the term 'cystosarcoma' in the context of phyllodes tumours.
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Affiliation(s)
- Puay Hoon Tan
- Department of Pathology, Singapore General Hospital, Singapore
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Poret H, Cormier B, Marret H, Body G, Ouldamer L. [Malignant myoepithelial breast carcinoma: diagnosis and therapeutic difficulties]. ACTA ACUST UNITED AC 2012; 41:334-7. [PMID: 22959079 DOI: 10.1016/j.gyobfe.2012.07.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2012] [Accepted: 05/04/2012] [Indexed: 01/18/2023]
Abstract
Myoepithelial carcinoma of the breast is a rare and malignant tumor. Local recurrence and distant metastasis are common. Treatment is not consensual. Here, we report a case of a 61-year-old female who developed a myoepithelial carcinoma. Primary treatment was a local wide excision with clear pathological margins. Three years later, a local recurrence was treated by further wide excision. Neither recurrences nor distant metastasis were detected four years later. Regular following of patients with myoepithelial carcinoma is essential.
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Affiliation(s)
- H Poret
- Service de gynécologie, centre Olympe-de-Gouges, CHU de Bretonneau, 2 boulevard Tonnelé, Tours, France
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Abstract
Epithelial-myoepithelial proliferations of the breast are a heterogeneous poorly defined group of lesions characterized morphologically by dual differentiation into ductal (luminal) and myoepithelial cells. They include neoplastic and non-neoplastic entities that have overlapping morphologic features that may give rise to diagnostic difficulty. Many of these entities are low grade or of uncertain malignant potential but the biology of some of these rare lesions remains to be elucidated. This article discusses the differential diagnosis of epithelial-myoepithelial lesions of the breast and highlights the morphologic features of some of these entities.
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Affiliation(s)
- Rola H Ali
- Department of Pathology, University of British Columbia and Consultant Pathologist, BC Cancer Agency, 600 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada
| | - Malcolm M Hayes
- Department of Pathology, University of British Columbia and Consultant Pathologist, BC Cancer Agency, 600 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada; Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC V6T 2B5, Canada.
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Yigit S, Pehlivan FS, Evcim G, Etit D. Clinicopathologic features of the mixed epithelial and mesenchymal type metaplastic breast carcinoma with myoepithelial differentiation in a subset of six cases. Pathol Res Pract 2012; 208:147-50. [DOI: 10.1016/j.prp.2011.12.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 11/30/2011] [Accepted: 12/28/2011] [Indexed: 10/28/2022]
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MicroRNA profiles of healthy basal and luminal mammary epithelial cells are distinct and reflected in different breast cancer subtypes. Breast Cancer Res Treat 2011; 130:735-45. [PMID: 21409395 DOI: 10.1007/s10549-010-1303-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Accepted: 12/08/2010] [Indexed: 10/18/2022]
Abstract
In order to determine the microRNA expression pattern in normal basal and luminal breast epithelium and to analyze the relationship of this expression pattern to different breast cancer subtypes, laser-microdissected luminal and basal cells isolated from plastic surgery tissue samples were used for comprehensive expression profiling, measuring 664 microRNAs by low-density TaqMan arrays. In a test (n = 5) and validation set (n = 9) 10 differentially expressed microRNAs were identified by TaqMan RT-qPCR. These microRNAs were studied in laser-microdissected cells of luminal A (n = 5), luminal B (n = 5), basal-like subtypes of breast cancer (n = 10), and malignant myoepithelioma of the breast (n = 10). From 116 microRNAs unequivocally expressed in normal breast epithelial cells, we identified 8 basal microRNAs (let7c, miR-125b, miR-126, miR-127-3p, miR-143, miR-145, miR-146b-5p, and miR-199a-3p), preferentially expressed in normal basal cells, exceeding luminal cells by a factor from 4 to 1000. All of these microRNAs were also found to be significantly elevated in malignant myoepithelioma but not in basal-type of breast cancer. Two members of the miR-200 family (miR-200c and miR-429) were predominantly luminal. Both microRNAs were expressed in the luminal and basal type of breast cancer in contrast to malignant myoepithelioma, which revealed significantly lower levels potentially contributing to its mesenchymal phenotype. In conclusion, normal luminal and basal mammary epithelial cells exhibit a different microRNA expression profile. Malignant myoepithelioma seems to exhibit a basal pattern of microRNA expression, whereas the so-called basal-like breast cancer is clearly different and reveals a luminal type pattern.
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