Metaplastic breast carcinoma: a cytohistologic and clinical study of 10 cases.

Metaplastic breast carcinomas (MBC) account for < 5% of breast malignancies and have an uncertain prognostic significance. The tumors tend to grow rapidly, and most are negative for hormone receptors. Adenosquamous carcinomas and various types of carcinosarcomas may be classified as MBC. We evaluated the cytologic, histologic, and clinical parameters of 10 MBC to determine important diagnostic features of these tumors. A cytologic diagnosis of MBC, based on the identification of two distinct malignant components, was made preoperatively in five of 10 (50%) cases, and retrospectively in two additional cases; two specimens were inadequately cellular. Poorly-differentiated adenocarcinoma was the most frequently encountered component of MBC. It is recommended that malignant breast aspirates be carefully scrutinized for multiple neoplastic components. Our series of MBC differs from previous reports in that two cases presented as inflammatory breast cancer, one case was pregnancy-associated, and there was a higher incidence of estrogen and progesterone receptor positivity. No cancer-related deaths occurred during a mean follow-up period of over 6 yr.