First reported case of a squamous cell carcinoma arising in the duodenum in a patient with Lynch syndrome.

A 58 y/o male with Lynch syndrome, who was diagnosed with a squamous cell carcinoma (SCC) arising in the duodenum, is described. Previous malignancies included two metachronous colorectal adenocarcinomas, and a known family history of Lynch syndrome associated with deletion of exons 8-15 of the MSH2 gene. Analysis of his small bowel SCC revealed loss of MSH2 and MSH6 protein expression, suggesting a pathogenic role of the germ-line deletion. While small bowel adenocarcinomas have previously been reported in Lynch syndrome, to our knowledge this is the first report of Lynch syndrome-associated squamous histology. As patients with Lynch syndrome live longer with early detection and treatment of their cancers, unusual sites and histology of previously unreported cancers may emerge. It is also important to recognize variant histologies that otherwise might not prompt pursuing a diagnosis of Lynch syndrome in the appropriate clinical setting.