Muir-Torre syndrome in a patient with advanced duodenal carcinoma.

Muir-Torre syndrome (MTS) is a rare autosomal dominant disorder characterized by sebaceous neoplasms and visceral malignancies and is regarded as a phenotypic variant of Lynch syndrome. Although colorectal and genitourinary cancers are the most common visceral malignancies in MTS, duodenal cancer is extremely rare. We report a case of advanced duodenal cancer associated with MTS treated with multidisciplinary therapy. A 62-year-old man with a history of multiple colorectal cancers and sebaceous carcinomas presented with vomiting and epigastric pain. Upper gastrointestinal endoscopy revealed a circumferential tumor with stenosis in the fourth portion of the duodenum, and a biopsy showed moderately differentiated adenocarcinoma. Computed tomography suggested peritoneal dissemination, and the tumor was considered unresectable. Systemic chemotherapy with 5-fluorouracil and oxaliplatin resulted in tumor regression and disappearance of the suspected dissemination. Conversion surgery with partial duodenectomy and lymph node dissection was subsequently performed, achieving R0 resection. Genetic testing revealed microsatellite instability-high status and a pathogenic MSH2 mutation, confirming MTS. Although postoperative lymph node recurrence occurred, the disease has been controlled with immunotherapy and radiotherapy, and the patient remains alive two years after surgery. This case highlights the potential role of multidisciplinary treatment and the importance of recognizing MTS and implementing appropriate surveillance.