Metaplastic breast cancer (MBC) is a rare, aggressive form of breast cancer first described by pathologists in 2000. It is usually discovered in advanced stages and has a low survival rate. It is divided into various subtypes: lowgrade adenosquamous, fibromatosis-like metaplastic, squamous cell, spindle cell, metaplastic with mesenchymal differentiation (including chondroid, osseous, or other types), mixed metaplastic, and myoepithelial carcinomas. Surgery is the treatment of choice, followed by adjuvant chemotherapy and/or radiotherapy. We present the case of a 44-year-old woman with metaplastic breast cancer, reviewing the characteristics of this condition, the particularities of the case, and the treatment chosen in this particular situation.