Sebaceous carcinoma of the breast.

Sebaceous carcinoma (SC) of the breast is a rare malignant tumor and only nine cases, including the present one, have been reported in the English-language literature. The present report describes a case of mammary SC in a 50-year-old Japanese woman. The tumor was gray-white on cut surface and separate from the skin and the nipple. Microscopically, lobules encircled by a fibrous envelope and cords or small cell nests in the stroma were noted. These two types of structures were composed of dark cells and clear foamy cells. The dark cells had large nuclei and amphophilic cytoplasm. The clear foamy cells had numerous lipid vacuoles, confirmed on immunostaining with anti-adipophilin antibody and electron microscopy. In the lobules the gradual transitions from basal dark cells to central clear foamy cells and comedo-like necrosis were observed. The tumor cells were positive on immunohistochemistry for cytokeratins (CAM5.2, AE1/AE3), Her2/neu and androgen receptor but negative for estrogen and progesterone receptors. This is the first case of an androgen receptor-positive mammary SC to be reported, and therefore contributes to the understanding of the clinicopathological features of SC of the breast.