Metaplastic breast carcinoma with chondrosarcomatous differentiation: an unusual disease with a worse prognosis

Metaplastic breast carcinoma (MBC) has an incidence of <1% of all breast cancers and MBC with chondrosarcomatous differentiation is even more rare, <0.1% of all cases. The World Health Organization have classified MBC into pure epithelial-type and mixed epithelial and mesenchymal type. The epithelial-type MBC is sub-classified into squamous cell carcinoma, adenosquamous carcinoma and adenocarcinoma with spindle cell differentiation; mixed type MBC is sub-classified into carcinosarcoma and carcinoma with osseous and chondroid metaplasia. Metaplastic carcinomas of the breast are characterized by large tumour size and rapid  growth, and they are usually estrogen receptor, progesterone receptor, and HER2/neu negative and tend to have a worse prognosis than other triple negative breast cancers. There is a noteworthy increased risk of tumour recurrence and a worse prognosis with MBC compared with invasive lobular carcinoma and infiltrating duct carcinoma. We report a case of metaplastic carcinoma with extensive chondroid differentiation that is chondrosarcoma and chondroid metaplasia along with classic infiltrating duct carcinoma with involvement of ipsilateral axillary lymph nodes.