Carcinosarcoma of the breast: report of two cases.

Carcinosarcoma is a rare, malignant tumor of the breast, consisting of intraductal or infiltrating carcinoma contiguous or subtly merged with a highly cellular, mitotically active pleomorphic spindle cell stroma (sarcoma). It is a form of the metaplastic mammary carcinomas and it is probably derived of myoepithelial cells. We report two cases of breast carcinosarcoma in two white women. The patients, following a frozen section positive for malignancy, had had a modified radical mastectomy. Paraffin sections and positive immunohistochemical cell staining (in our first case) confirmed the diagnosis of carcinosarcoma. This tumor should be distinguished from other forms of metaplastic carcinomas because it is very aggressive and has an ominous prognosis.