Extraocular Sebaceous Carcinoma in situ Concurrent with Actinic Keratosis: A Case Report and Review of the Literature

Sebaceous carcinoma is a malignant neoplasm frequently classified as periocular or extraocular. Extraocular sebaceous carcinoma is a relatively rare tumor commonly appearing in the head and neck region. Furthermore, extraocular sebaceous carcinoma limited to the epithelium, which is called ‘extraocular sebaceous carcinoma in situ’ is extremely rare with less than 10 cases reported in the literature. Herein, we present the case of a 93-year-old female who diagnosed as extraocular sebaceous carcinoma in situ occurring concurrently with actinic keratosis. In the present case, extraocular sebaceous carcinoma in situ as identified without any connection to an adnexal component but concurrent with actinic keratosis. This case is evidence that extraocular sebaceous carcinoma can arise from the epidermis and the tumor cells of intraepidermal squamous neoplasia can differentiate toward malignant sebocytes. (Korean J Dermatol 2021;59(4):307∼309)