Histiocytoid carcinoma: a variant of breast cancer.

The history of a patient presenting with metachronous bilateral breast cancer displaying histiocytoid features is reviewed. Although regional metastases were noted, this patient has not demonstrated an aggressive systemic disease pattern. In the past, histiocytoid breast cancer has been classified as either a lipid-rich carcinoma or as a variant of lobular carcinoma. However, histiocytoid carcinoma should be considered a distinct entity. Unlike the lipid-rich carcinomas, this tumor stained strongly for mucin. Immunoperoxidase staining indicated strong positively for CEA and negative staining for alpha-lactalbumin. There is suggestive evidence of a relationship between histiocytoid breast carcinoma and breast cancers of apocrine origin. Controversy remains and further evaluation is needed to elucidate the histiogenesis and biological potential of this neoplasm.