The sebaceous proliferations seen in patients with Muir-Torre syndrome are unique and difficult to classify. Having reviewed over 50 skin biopsies from five patients with Muir-Torre syndrome, we conclude that the primary proliferation involves the hair follicle and most often resembles either a keratoacanthoma or a sebaceous proliferation, but may have histologic features of both lesions. Unusual patterns seen in the sebaceous components may include solid basaloid sheets, mucinous areas, and convoluted glands.