Intraductal papillary mucinous neoplasm of the pancreas with loss of mismatch repair in a patient with Lynch syndrome.

Intraductal papillary mucinous neoplasm (IPMN) of the pancreas is a precancerous lesion with a well-described progression to carcinoma. This case report describes a 61-year-old woman with a history significant for multiple cancers and a confirmed germline mutation of MSH2, a mismatch repair gene responsible for Lynch syndrome, who was also found to have an IPMN of the pancreas. Phenotypic manifestations of Lynch syndrome in this patient included multiple adenomas and adenocarcinomas of the colon and also several other Lynch syndrome-associated cancers. The patient's adenocarcinoma of the colon and IPMN of the pancreas showed identical immunohistochemical staining profiles with loss of expression of MSH2 and MSH6 proteins and high levels of microsatellite instability. The immunohistochemical staining and microsatellite instability patterns of the adenocarcinoma of the colon and IPMN gives strong evidence to support the consideration of IPMN as part of the spectrum of lesions found in Lynch syndrome.