Abstract
BACKGROUND: Sebaceous carcinoma of the breast is a distinct variant of invasive ductal carcinoma. It is rare and only several cases have been reported. CASE PRESENTATION: An 80-year-old woman noted bloody discharge from her left nipple and palpated a lump in her left breast. Ultrasonography revealed a 19-mm mass in the left breast. Fine-needle aspiration suggested invasive ductal carcinoma. Partial mastectomy and sentinel lymph node biopsy were performed. On histological examination, the tumor revealed solid growth of small, round uniform cells with clear cytoplasm, partially intermingled with vacuolated cells indicative of sebaceous differentiation. The tumor cells contained abundant Sudan Black B-positive lipid droplets in the cytoplasm, and they were immunohistochemically positive for adipophilin. They were negative for estrogen receptor, progesterone receptor, and androgen receptor; positive for cytokeratin 7 and Ber-EP4; and partially positive for epithelial membrane antigen. Based on these findings, the patient was diagnosed with sebaceous carcinoma of the breast. CONCLUSIONS: We diagnosed a rare case of sebaceous carcinoma of the breast.