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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.
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).
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).
Most cancers start in the ducts and drain first to the axillary nodes, which is why the armpit is checked and a sentinel node is sampled.
Same organ: Triple-negative breast cancer (TNBC), Breast cancer (all types), HR-positive / HER2-negative breast cancer, HER2-positive breast cancer, Male breast cancer, Ductal carcinoma in situ (DCIS), High-risk early HR-positive breast cancer, HR-positive metastatic breast cancer after CDK4/6 inhibitors, HER2-low and HER2-ultralow metastatic breast cancer, Early HER2-positive breast cancer, HER2-positive breast cancer with brain metastases, Early triple-negative breast cancer, Metastatic triple-negative breast cancer, Basal-like 1 triple-negative breast cancer (BL1), Basal-like 2 triple-negative breast cancer (BL2), Mesenchymal triple-negative breast cancer (M), Mesenchymal stem-like triple-negative breast cancer (MSL), Luminal androgen receptor triple-negative breast cancer (LAR), Immunomodulatory triple-negative breast cancer (IM), Carcinoma with medullary pattern (medullary breast cancer), Adenoid cystic carcinoma of the breast, Apocrine carcinoma of the breast, Secretory carcinoma of the breast, BRCA-associated triple-negative breast cancer, Inflammatory breast cancer, Paget disease of the nipple, Phyllodes tumour of the breast, Invasive lobular carcinoma of the breast, Invasive breast carcinoma of no special type (invasive ductal carcinoma), Tubular carcinoma of the breast, Mucinous carcinoma of the breast, Papillary carcinomas of the breast (encapsulated, solid and invasive papillary), Invasive cribriform carcinoma of the breast, Invasive breast carcinoma with medullary pattern (medullary carcinoma), Invasive micropapillary carcinoma of the breast, Neuroendocrine neoplasms of the breast, Lobular carcinoma in situ (LCIS)
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.
As for metastatic triple-negative disease (pembrolizumab where PD-L1 positive, TROP2 ADCs); response to chemotherapy is poorer than in other triple-negative cancers.
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Query for this cancer: (TITLE:"Metaplastic breast carcinoma" OR ABSTRACT:"Metaplastic breast carcinoma" OR TITLE:"Metaplastic carcinoma of the breast" OR ABSTRACT:"Metaplastic carcinoma of the breast" OR TITLE:"MpBC" OR ABSTRACT:"MpBC" OR TITLE:"Spindle cell carcinoma of the breast" OR ABSTRACT:"Spindle cell carcinoma of the breast" OR TITLE:"Matrix-producing carcinoma" OR ABSTRACT:"Matrix-producing carcinoma" OR TITLE:"Squamous cell carcinoma of the breast" OR ABSTRACT:"Squamous cell carcinoma of the breast") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Metaplastic breast carcinoma, not a curated reading list.
The targets of this cancer's medicines and the ones linked to it directly.
Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record.
One section per setting: the options named, what each is for, the trials behind them, the recorded trade-offs and the questions to ask.
Bleeding that will not stop, black or bloody stools, or unexplained bruising when platelets are expected to be low.
Persistent headache with extreme tiredness, nausea, dizziness on standing or low blood pressure. Vomiting, severe weakness or collapse is adrenal crisis.
Blisters, peeling, or sores in the mouth or eyes with a rash. Enfortumab vedotin carries a boxed warning for Stevens-Johnson syndrome and toxic epidermal necrolysis, mostly in the first cycle.
No pharmacokinetic interactions expected (antibody). See the irAE guide for toxicity management.
UGT1A1*28 homozygotes: higher neutropenia risk; G-CSF prophylaxis is often used.
Dose by Calvert formula using GFR (see the calculators).
See all on the product pages:CarboplatinPaclitaxel / nab-paclitaxelPembrolizumabSacituzumab govitecan·Printable cards in the navigator
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