{"entity":{"id":"metaplastic-breast-carcinoma","kind":"cancer","name":"Metaplastic breast carcinoma","aka":["Metaplastic carcinoma of the breast","MpBC","Spindle cell carcinoma of the breast","Matrix-producing carcinoma","Squamous cell carcinoma of the breast","Low-grade adenosquamous carcinoma","Fibromatosis-like metaplastic carcinoma","Carcinosarcoma of the breast"],"tldr":"Metaplastic breast cancer is a rare form in which part of the tumour has changed into another tissue type, such as squamous skin-like cells, spindle cells or bone and cartilage. Most are triple-negative and they do worse than other triple-negative cancers, resisting chemotherapy; the low-grade forms are an exception with an excellent outlook.","summary":"Metaplastic breast cancer is defined by the histological presence of at least two cellular types, typically epithelial and mesenchymal components, and the WHO classification (5th edition, 2019) lists low-grade adenosquamous carcinoma, fibromatosis-like metaplastic carcinoma, squamous cell carcinoma, spindle cell carcinoma, metaplastic carcinoma with heterologous mesenchymal differentiation (chondroid, osseous) and mixed forms (Tan 2020; Cserni 2020). It carries a triple-negative phenotype yet a worse prognosis and shorter survival than triple-negative disease of no special type, with recurrent alterations in epithelial-to-mesenchymal transition, EGFR amplification, PI3K/Akt, Wnt/beta-catenin and cell-cycle pathways, and no standardised treatment guideline of its own (Reddy 2020). In the National Cancer Data Base, five-year overall survival was 72.7 percent for metaplastic against 87.5 percent for non-metaplastic disease overall and 71.1 against 77.8 percent among triple-negative patients; within metaplastic disease receptor status did not change survival (hazard ratio 1.16); patients more often had mastectomy (59.0 against 44.9 percent), chemotherapy (74.1 against 43.1 percent) and axillary dissection, and more often had negative nodes (20.0 against 10.6 percent); chemotherapy (hazard ratio 0.69) and radiotherapy (0.52) were associated with better survival, axillary dissection with worse (Ong 2018). The claudin-low intrinsic subtype has a high frequency of metaplastic differentiation (Prat 2010). Two members of the family are indolent: fibromatosis-like metaplastic carcinoma and low-grade adenosquamous carcinoma, which the European Working Group for Breast Screening Pathology lists among the triple-negative special types unlikely to benefit from chemotherapy (Cserni 2021).","asOf":"2026-09-24","wikipedia":"https://en.wikipedia.org/wiki/Metaplastic_carcinoma","links":[{"label":"Reddy, Breast Cancer Res 2020: a comprehensive overview of metaplastic breast cancer","url":"https://doi.org/10.1186/s13058-020-01353-z"},{"label":"Ong, Ann Surg Oncol 2018: metaplastic breast cancer treatment and outcomes in 2,500 patients (National Cancer Data Base)","url":"https://doi.org/10.1245/s10434-018-6533-3"},{"label":"Tan, Histopathology 2020: the 2019 WHO classification of tumours of the breast","url":"https://doi.org/10.1111/his.14091"},{"label":"Cserni, Pathologica 2020: histological type and typing of breast carcinomas and WHO classification changes","url":"https://doi.org/10.32074/1591-951x-1-20"},{"label":"Cserni, Cancers 2021: triple-negative breast cancer histological subtypes with a favourable prognosis (European Working Group for Breast Screening Pathology)","url":"https://doi.org/10.3390/cancers13225694"},{"label":"Prat, Breast Cancer Res 2010: phenotypic and molecular characterisation of the claudin-low intrinsic subtype","url":"https://doi.org/10.1186/bcr2635"}],"tags":["breast","tnbc","subtype-page"],"related":["tnbc","tnbc-mesenchymal","medullary-pattern-breast-carcinoma"],"cancers":[],"sections":[],"technologies":[],"targets":["egfr"],"drugs":[],"companies":[],"institutions":[],"pathways":["emt","pi3k-akt-mtor"],"terms":["claudin-low","tumour-grade"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"group":"breast","burden":"Under 1 percent of breast cancers: 2,451 metaplastic against 568,057 non-metaplastic stage I to III cases in the US National Cancer Data Base, 2010 to 2014, of which 70.3 percent were triple-negative (Ong 2018).","subtypes":["Squamous cell carcinoma of the breast (ductal origin, no special type component often present)","Spindle cell carcinoma","Metaplastic carcinoma with chondroid or osseous (matrix-producing) differentiation","Low-grade adenosquamous carcinoma (indolent)","Fibromatosis-like metaplastic carcinoma (indolent)","Mixed metaplastic carcinoma"],"biomarkers":["Triple-negative receptor status (70.3 percent)","Mesenchymal or squamous component on histology (with cytokeratin and p63 immunostains)","EGFR amplification, PIK3CA and TP53 mutations (research)"],"standardOfCare":[{"setting":"Early disease","approach":"Surgery and radiotherapy, with chemotherapy as for triple-negative disease of no special type; chemotherapy and radiotherapy were associated with better survival in the national database, and axillary dissection was not. Low-grade adenosquamous and fibromatosis-like forms are treated by surgery alone in the European working group's consensus.","refs":["mastectomy","lumpectomy","sentinel-node","carboplatin","paclitaxel"]},{"setting":"Advanced disease","approach":"As for metastatic triple-negative disease (pembrolizumab where PD-L1 positive, TROP2 ADCs); response to chemotherapy is poorer than in other triple-negative cancers.","refs":["pembrolizumab","sacituzumab-govitecan"]}],"stateOfArt":[],"history":[],"pipeline":[],"openProblems":[],"parent":"tnbc"},"route":"/cancers/metaplastic-breast-carcinoma/","neighbours":{"cancer":[{"id":"medullary-pattern-breast-carcinoma","kind":"cancer","name":"Carcinoma with medullary pattern (medullary breast cancer)","route":"/cancers/medullary-pattern-breast-carcinoma/"},{"id":"breast-carcinoma-medullary-pattern","kind":"cancer","name":"Invasive breast carcinoma with medullary pattern (medullary carcinoma)","route":"/cancers/breast-carcinoma-medullary-pattern/"},{"id":"tnbc-mesenchymal","kind":"cancer","name":"Mesenchymal triple-negative breast cancer (M)","route":"/cancers/tnbc-mesenchymal/"},{"id":"tnbc","kind":"cancer","name":"Triple-negative breast cancer (TNBC)","route":"/cancers/tnbc/"}],"target":[{"id":"egfr","kind":"target","name":"EGFR","route":"/targets/egfr/"}],"pathway":[{"id":"emt","kind":"pathway","name":"Epithelial-mesenchymal transition & drug efflux","route":"/pathways/emt/"},{"id":"pi3k-akt-mtor","kind":"pathway","name":"PI3K / AKT / mTOR","route":"/pathways/pi3k-akt-mtor/"}],"term":[{"id":"claudin-low","kind":"term","name":"Claudin-low breast cancer","route":"/terms/claudin-low/"},{"id":"tumour-grade","kind":"term","name":"Grade","route":"/terms/tumour-grade/"},{"id":"lumpectomy","kind":"term","name":"Lumpectomy (breast-conserving surgery)","route":"/terms/lumpectomy/"},{"id":"mastectomy","kind":"term","name":"Mastectomy","route":"/terms/mastectomy/"}],"technology":[{"id":"sentinel-node","kind":"technology","name":"Sentinel lymph node biopsy","route":"/technologies/sentinel-node/"}],"drug":[{"id":"carboplatin","kind":"drug","name":"Carboplatin","route":"/drugs/carboplatin/"},{"id":"paclitaxel","kind":"drug","name":"Paclitaxel / nab-paclitaxel","route":"/drugs/paclitaxel/"},{"id":"pembrolizumab","kind":"drug","name":"Pembrolizumab","route":"/drugs/pembrolizumab/"},{"id":"sacituzumab-govitecan","kind":"drug","name":"Sacituzumab govitecan","route":"/drugs/sacituzumab-govitecan/"}]}}