Ocular and extraocular sebaceous carcinomas: A retrospective study with emphasis on the presence of in situ lesion and discussion and review of the histogenesis of extraocular sebaceous carcinoma

Sebaceous carcinoma (SC) is a rare carcinoma classified as ocular or extraocular. Ocular SC is believed to arise from the meibomian glands or the glands of Zeis. However, the origin of extraocular SC is controversial because there is no evidence of carcinoma arising from pre-existing sebaceous glands. Several hypotheses about the origin of extraocular SC have been proposed, including one suggesting an origin from intraepidermal neoplastic cells. Although extraocular SCs have been shown to occasionally comprise intraepidermal neoplastic cells, no study has investigated whether intraepidermal neoplastic cells possess sebaceous differentiation. The present study analyzed the clinicopathological features of ocular and extraocular SC, with an emphasis on the presence of in situ (intraepithelial) lesions. It retrospectively reviewed the clinicopathological features of eight patients with ocular and three patients with extraocular SC (eight women and three men; median age, 72 years), respectively. In situ (intraepithelial) lesions were observed in four of the eight ocular SC cases and one of the three extraocular SC cases and an apocrine component was noted in one patient with ocular SC (seboapocrine carcinoma). In addition, immunohistochemical analyses showed that the androgen receptor (AR) was expressed in all ocular SCs and two of the three extraocular SC cases. Adipophilin expression was observed in all ocular and extraocular SC. In situ lesions of extraocular SC showed positive immunoreactivity for both AR and adipophilin. The present study is the first to demonstrate sebaceous differentiation in in situ lesions of extraocular SC. The possible origin of extraocular SC is speculated to be the progenitor cells present in the sebaceous duct or interfollicular epidermis. The results of the present study and reported cases of SC in situ indicate that extraocular SC also arises from intraepidermal neoplastic cells.