Ten cases of sebaceous carcinoma arising in nevus sebaceus

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Abstract
Although nevus sebaceus is known to develop various types of secondary neoplasms, it rarely causes carcinoma and only 14 cases of secondary sebaceous carcinoma have been reported. In this study, 10 cases of sebaceous carcinoma arising in nevus sebaceus were collected. The clinicopathological features and results of immunohistochemical examinations with adipophilin, perilipin and p53 were summarized. Sebaceous carcinoma arising in nevus sebaceous predominantly occurred on the scalp (8/10) of elderly women (mean age, 67.7 years). No case was associated with Muir–Torre syndrome. We found several pathological features of sebaceous carcinoma; that is, made up mainly of germinative cells, moderate nuclear atypia without pleomorphism and many mitoses (4–28/10 high‐power field). Adipophilin and perilipin antibodies highlighted lipid drops in the cytoplasm of the malignant cells in all cases. Overexpression of p53 was seen in all cases. In two cases there were coexisting benign‐looking sebaceous lesions at the periphery of the main cancer nodule, and in these lesions p53 showed low positivity compared with the clearly malignant area. There was co‐occurrence of another neoplasm in three cases with trichoblastoma, sebaceoma and syringocystadenoma papilliferum, respectively. All cases were treated by excision of the malignant lesion, with or without inclusion of the nevus sebaceus. In a follow‐up period of 1–7 years, there was no case of recurrence, lymph node metastases or distant metastases. With these specific pathological and immunohistochemical findings using adipophilin, perilipin and p53, we have to consider the possibility that there is a tendency to underdiagnose secondary sebaceous carcinomas in nevus sebaceus. These clinicopathological features of sebaceous carcinomas developing in the nevus sebaceus seem to indicate different biological entities from de novo sebaceous carcinoma.