Extraocular Sebaceous Carcinoma in the Lower Back: Rare Presentation of a Great Masquerader

Abstract

Malignant adnexal tumors of the skin are rare. Sebaceous carcinoma (SC) is an aggressive malignant tumor of the sebaceous glands. It is traditionally classified into periocular and extraocular types. We present a rare case of extraocular SC of a 38-year-old female who presented with nontender swelling over the right flank for 1 year. Clinically, it was diagnosed with a sebaceous cyst. The tumor was excised and sent for histopathological examination. Sections showed sheets and lobules of tumor cells separated by fibrovascular stroma. Individual tumor cells were atypical basaloid to clear cells with prominent pleomorphism. Mitosis was brisk with areas of necrosis. On immunohistochemistry, the tumor cells were focally positive for epithelial membrane antigen and negative for S100 and PAX8 with a high Ki-67 index of 80%. Her postoperative period and follow-up for 1 year have been uneventful. This case is being reported for its rarity.

Keywords

• adnexal tumor
• extraocular
• immunohistochemistry
• sebaceous carcinoma