Muir-Torre syndrome: a rare but important disorder.

Muir-Torre syndrome (MTS) is a rare disorder characterized by the presence of at least one sebaceous gland neoplasm and at least one visceral malignancy. Sebaceous adenomas, sebaceous carcinomas, and sebaceomas (sebaceous epitheliomas) are all characteristic glandular tumors of MTS. The most common visceral malignancies associated with MTS are colorectal, followed by genitourinary. These visceral malignancies frequently have a more indolent course in patients with MTS than they would otherwise. Muir-Torre syndrome is an autosomal dominant disorder; however, sporadic cases are known to develop. It often is associated with germ-line mutations in the mutS homolog 2, colon cancer, nonpolyposis type 1 (Escherichia coli) gene, MSH2, and the mutL homolog 1, colon cancer, nonpolyposis type 2 (E. coli) gene, MLH1 (similar to hereditary nonpolyposis colon cancer [HNPCC]). The diagnosis of MTS currently is based on clinical criteria; however, immunohistochemical staining for MSH2 and MLH1 can confirm the diagnosis. We report 2 patients with MTS who developed colon adenocarcinomas in conjunction with sebaceous carcinomas. Both patients demonstrated loss of MSH2 expression in tumor cells on immunohistochemical staining. One of these patients later developed gastric carcinoma, a very uncommon malignancy associated with MTS. We conclude that the diagnosis of rare sebaceous lesions associated with MTS may represent a marker of visceral disease and warrants further investigation for internal malignancies in the individual and at-risk family members.