Clinicopathological and immunohistochemical features of a sebaceous carcinoma arising within a benign dermoid cyst of the ovary.

Pure sebaceous neoplasms arising in dermoid cysts of the ovary are exceedingly rare. A 63-year-old female with abdominal swelling and pain underwent a right salpingo-oophorectomy that showed a unilocular cyst weighing 830 g and measuring 15x12x10 cm, filled with sebaceous material containing a few hair shafts. The cyst wall exhibited plaques protruding into the cavity of the cyst. Microscopy revealed a dermoid cyst with nests and lobules of atypical and infiltrating sebaceous cells surrounded by basaloid cells. The tumor cells stained diffusely for high-molecular-weight cytokeratins and focally for cytokeratin 7, cytokeratin 19, epithelial membrane antigen and carcinoembryonic antigen in the immunohistochemistry study. Low-molecular-weight cytokeratins, cytokeratin 20, vimentin, S100, p63, estrogen receptor, progesterone receptor, p53 and c-erbB-2 were negative in tumoral cells. The proliferative labeling index (Ki67 and proliferating cell nuclear antigen) was low. Basal cell carcinoma with sebaceous differentiation and sebaceoma must be considered in the differential diagnosis. However, the presence of obvious malignant sebaceous differentiation in nearly every tumor nest and lack of peripheral palisading and peri-tumoral myxoid stroma excluded these diagnoses. Some histogenetic concepts relevant to this case are discussed along with a brief review of this neoplasm. To our knowledge, this is the sixth case report of a sebaceous carcinoma arising in a mature cystic teratoma of the ovary.