Analysis of Sebaceous Neoplasms for DNA Mismatch Repair Proteins in Muir-Torre Syndrome

Muir-Torre syndrome is a rare genodermatosis inherited most frequently in an autosomal dominant fashion. Current criteria for its diagnosis include at least one sebaceous tumor and an underlying visceral malignancy. Muir-Torre syndrome is strongly associated with a germline mutation in DNA mismatch repair genes. We report two patients with a history of colorectal carcinoma who presented with sebaceous neoplasms on the face and trunk. Immunohistochemical staining of the sebaceous neoplasms demonstrated absence of mismatch repair proteins MSH2 and MSH6. Genetic studies confirmed deletions in the MSH2 gene, and a diagnosis of Lynch syndrome was made. Immunohistochemical staining for mismatch repair genes MLH1, MSH2, MSH6 and PMS2 may aid in the diagnosis of Muir-Torre syndrome in cases where there is high suspicion. Genetic testing is an important final step in the confirmation of Muir-Torre syndrome.