Metaplastic carcinoma is a group of breast cancers characterized by epithelial cells that show differentiation towards squamous cells, or mesenchymal-looking elements such as spindle, chondroid, osseous, and rhabdoid cells. It is a rare form of cancer accounting for less than 1% of all breast cancers. The morphology depends on the line of differentiation. Most cases are negative for ER, PR, and HER2, but cytokeratin expression should still be present.