First case report of Muir-Torre syndrome associated with non-small cell lung cancer.

The eponymous Muir-Torre syndrome (MTS) is a clinical variant of hereditary non polyposis colorectal cancer, and is defined as an autosomal dominant condition with simultaneous sebaceous neoplasms of the skin and visceral malignant disease resulting from germline mutations in the DNA mismatch repair (MMR) genes. To date the most common visceral malignancy described is colorectal cancer, which is seen in approximately 50% of cases. Other clearly associated tumours include endometrial adenocarcinomas, urothelial transitional cell carcinomas, upper gastrointestinal adenocarcinomas, sebaceous adenomas and ovarian (often mucinous) carcinomas. Here we report the first recorded case of adenocarcinoma of the lung with loss of MMR gene function to be identified in a patient with MTS. The MMR deficient lung tumour demonstrated less aggressive clinical behaviour compared with a synchronous MMR proficient lung adenocarcinoma.