Blaire A. Anderson, Shaofeng Yan and Bing Ren
Sebaceous adenoma is a rare cutaneous neoplasm. It typically presents in the sixth decade of life and beyond as a yellow or tan-pink papule in sun-exposed areas, particularly the head and neck. Though sebaceous adenoma is widely considered a benign entity, it can be a presenting condition in patients with Muir-Torre Syndrome (MTS), a rare subtype of Hereditary Nonpolyposis Colorectal Cancer (HNPCC), characterized by an increased risk for visceral malignancies and the development of sebaceous neoplasms. HNPCC and MTS result from germline mutations in DNA Mismatch Repair (MMR) protein genes including MLH1, PMS2, MSH2, MSH6, and EPCAM. Cases of sebaceous adenoma arising in non-sun-exposed areas in patients under 60 years of age with personal or family histories suggestive of HNPCC/MTS are routinely evaluated for loss of Deoxyribonucleic Acid (DNA) mismatch repair proteins and possible germline mutations. Here we present a rare case of penile sebaceous adenoma with unusual histologic features and sporadic loss of MLH1 and PMS2 protein expression in a 52-year-old patient.
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