# Metaplastic breast carcinoma

Source: https://onco.cc/cancers/metaplastic-breast-carcinoma/  
OnCo record `metaplastic-breast-carcinoma` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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).

## Fields

- Kind: Cancer
- Last checked: 2026-09-24
- Also known as: 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
- Tags: breast; tnbc; subtype-page
- 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)

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/metaplastic-breast-carcinoma/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/metaplastic-breast-carcinoma/#overview
- What it is (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/metaplastic-breast-carcinoma/#what-it-is [6 subtypes]
- Finding it (on the hub): How it shows itself, how it is confirmed, what screening exists, and the biomarkers clinicians test for. https://onco.cc/cancers/metaplastic-breast-carcinoma/#finding-it [3 biomarkers]
- Treating it (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/metaplastic-breast-carcinoma/#treating-it [2 settings, 2 decisions with options]
- Evidence (on the hub): Trials recruiting now, the landmark trials, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/metaplastic-breast-carcinoma/#evidence
- The science (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/metaplastic-breast-carcinoma/#science [3 targets, 2 pathways]
- Where you are (own page): Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record. https://onco.cc/cancers/metaplastic-breast-carcinoma/where-you-are/
- Living with it (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/metaplastic-breast-carcinoma/#living-with-it [10 questions, 6 red cards]
- What is coming (own page): Everything in development, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/metaplastic-breast-carcinoma/coming/ [4 medicines]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/metaplastic-breast-carcinoma/data/ [23 connected records]

## Standard of care

- Early disease: 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. ([Mastectomy](https://onco.cc/terms/mastectomy/), [Lumpectomy (breast-conserving surgery)](https://onco.cc/terms/lumpectomy/), [Sentinel lymph node biopsy](https://onco.cc/technologies/sentinel-node/), [Carboplatin](https://onco.cc/drugs/carboplatin/), [Paclitaxel / nab-paclitaxel](https://onco.cc/drugs/paclitaxel/))
- Advanced disease: As for metastatic triple-negative disease (pembrolizumab where PD-L1 positive, TROP2 ADCs); response to chemotherapy is poorer than in other triple-negative cancers. ([Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Sacituzumab govitecan](https://onco.cc/drugs/sacituzumab-govitecan/))

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Metaplastic_carcinoma
- Reddy, Breast Cancer Res 2020: a comprehensive overview of metaplastic breast cancer: https://doi.org/10.1186/s13058-020-01353-z
- Ong, Ann Surg Oncol 2018: metaplastic breast cancer treatment and outcomes in 2,500 patients (National Cancer Data Base): https://doi.org/10.1245/s10434-018-6533-3
- Tan, Histopathology 2020: the 2019 WHO classification of tumours of the breast: https://doi.org/10.1111/his.14091
- Cserni, Pathologica 2020: histological type and typing of breast carcinomas and WHO classification changes: https://doi.org/10.32074/1591-951x-1-20
- Cserni, Cancers 2021: triple-negative breast cancer histological subtypes with a favourable prognosis (European Working Group for Breast Screening Pathology): https://doi.org/10.3390/cancers13225694
- Prat, Breast Cancer Res 2010: phenotypic and molecular characterisation of the claudin-low intrinsic subtype: https://doi.org/10.1186/bcr2635

## Connected records

- cancers: [Carcinoma with medullary pattern (medullary breast cancer)](https://onco.cc/cancers/medullary-pattern-breast-carcinoma/), [Invasive breast carcinoma with medullary pattern (medullary carcinoma)](https://onco.cc/cancers/breast-carcinoma-medullary-pattern/), [Mesenchymal triple-negative breast cancer (M)](https://onco.cc/cancers/tnbc-mesenchymal/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- targets: [EGFR](https://onco.cc/targets/egfr/)
- pathways: [Epithelial-mesenchymal transition & drug efflux](https://onco.cc/pathways/emt/), [PI3K / AKT / mTOR](https://onco.cc/pathways/pi3k-akt-mtor/)
- terms: [Claudin-low breast cancer](https://onco.cc/terms/claudin-low/), [Grade](https://onco.cc/terms/tumour-grade/), [Lumpectomy (breast-conserving surgery)](https://onco.cc/terms/lumpectomy/), [Mastectomy](https://onco.cc/terms/mastectomy/)
- technologies: [Sentinel lymph node biopsy](https://onco.cc/technologies/sentinel-node/)
- drugs: [Carboplatin](https://onco.cc/drugs/carboplatin/), [Paclitaxel / nab-paclitaxel](https://onco.cc/drugs/paclitaxel/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Sacituzumab govitecan](https://onco.cc/drugs/sacituzumab-govitecan/)

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JSON: https://onco.cc/api/v1/entities/metaplastic-breast-carcinoma.json