Muir-Torre syndrome--a phenotypic variant of Lynch syndrome

Muir-Torre syndrome (MTS) represents an autosomal dominantly inherited condition and is considered a phenotypic variant of the more common hereditary nonpolyposis colorectal cancer syndrome (HNPCC), or Lynch syndrome. MTS combines at least one cutaneous neoplasm with sebaceous differentiation (e.g. sebaceoma, sebaceous adenoma, and sebaceous carcinoma), and at least one visceral malignancy. MTS is a genetic disorder caused by a germline mutation in one of the DNA mismatch repair (MMR) genes. Tumors in MTS patients are characteristically associated with the loss of MMR protein expression and/or microsatellite instability (70%). Patients who are suspected to have MTS/Lynch syndrome are often identified by dermatologists, dermatopathologists/pathologists, gastroenterologists and gynecologists. If MTS is suspected on a clinicopathological ground, necessary additional laboratory investigations should be performed only in specialized pathological departments providing immunohistochemistry and molecular biologic analysis service.