Considerations on the Performance of Immunohistochemistry for Mismatch Repair Gene Proteins in Cases of Sebaceous Neoplasms and Keratoacanthomas With Reference to Muir-Torre Syndrome

Cutaneous sebaceous tumors, as well as keratoacanthomas, are associated with Muir-Torre syndrome (MTS). Visceral neoplasias are a feature of this syndrome; thus, early detection using a cutaneous biopsy is very important in dermatopathology. A dermatopathologist can apply different techniques in such cases, including immunohistochemistry for several mismatch repair proteins or molecular studies for microsatellites instability. However, in a world where economic resources play an increasing role, how discriminative the dermatopathologist should be in investigating cutaneous lesions that may indicate MTS is not a trivial matter. Although previous reports have presented algorithms on MTS focusing on a multidisciplinary approach, our report emphasizes the role of the dermatopathologist and tries to answer several questions that could arise when facing a cutaneous tumor that may indicate MTS.