Abstract
Collision tumors are neoplasms composed of two or more distinct cellular lineages coexisting at the same anatomic site. Incomplete biopsy, partial pathological slide examination or failure to include this diagnosis into the clinical differential may complicate and delay appropriate therapy. Although collision tumors are well documented, basal cell carcinoma (BCC) occurring with sebaceous carcinoma (SC) has only been reported in a single case report. The aim of the authors is to present a case of collision BCC and SC to highlight a rare clinicopathological case. We also present this case to advise caution to detect mimickers of BCC that warrant greater clinical workup and use this case to emphasize the importance of Mohs micrographic surgery for the treatment of SC.