Histiocytoid breast cancer: an uncommon histologic variant of lobular carcinoma.

We present a case of histiocytoid breast cancer (HBC), which is a rare variant of breast carcinoma. The patient underwent an excisional biopsy for a palpable mass in her right breast. The neoplastic cells exhibited pronounced histiocytoid appearance. Immunohistochemical and histochemical studies were performed and tumor cells were positive for PAS, keratin PAN-CK, EMA, progesterone (PgR) and estrogen receptors (ER), while S-100 protein, CD68, CEA, and c-erbB2 were negative. Differential diagnosis issues and immunohistochemical data are emphasized and the literature is reviewed.