Two histopathologic patterns of well-differentiated extraocular sebaceous carcinoma

Background: No previous reports on the variation in the histopathological patterns of well-differentiated sebaceous carcinoma are yet to be published. Methods: We reviewed the histopathology of six examples of well-differentiated extraocular sebaceous carcinoma. Results: Two distinct histopathological patterns of sebaceous carcinoma, namely a secretory pattern (N = 2) and a non-secretory pattern (N = 4), were defined. The secretory pattern is typified by sebaceous lobular architecture with focal holocrine secretion, whereas the non-secretory pattern lacks this organoid quality. Both carcinomas with the secretory pattern showed low-grade cytological atypia, whereas the four carcinomas with the non-secretory pattern included three lesions with high-grade cytological atypia. A sebaceous adenoma-like area was seen in both secretory pattern carcinomas, whereas a focus of intraepithelial sebaceous carcinoma (sebaceous carcinoma in situ) was seen in two of the non-secretory pattern carcinomas. Conclusions: The clinicopathological significance of the two histopathological patterns remains unclear, because the number of reported cases is limited. It is possible that these two histopathological patterns of carcinoma have different histogenetic and prognostic implications, but no definitive conclusions can be made until further studies of a larger number of cases can be completed.