Serous oligocystic adenoma (SOIA) of the pancreas--first reported case of a genetically fixed association in a patient with hereditary non-polyposis colorectal cancer (HNPCC).

Cystic tumor lesions of the pancreas are relatively uncommon. Advances in imaging and pathohistology, including immunohistochemistry, have led to the detection and classification of novel tumor entities. A promoting aspect is the extended indication profile in pancreatic surgery, in particular, because of lower perioperative morbidity and mortality. One of these classified cystic neoplasms of the pancreas is serous oligocystic adenoma (SOIA), a rare and benign tumor lesion. We report on a 41-year-old man with a cystic lesion within the pancreatic head. Therefore, he underwent pylorus-preserving cephal duodenopancreatectomy. Pathohistologic investigation revealed a SOIA. He had a medical history significant for subtotal colectomy because of a synchronous double colonic carcinoma. Both tumor tissue specimens had been characterized for a high level of microsatellite instability (MSI) and loss of hMLH1, as well as for a corresponding germ line mutation in hMLH1 gene, leading to the diagnosis of hereditary non-polyposis associated colon cancer (HNPCC). The case is remarkable since the SOIA revealed MSI and loss of hMLH1 protein in the tumor cells that has never been reported for this tumor type. In addition, there is a rare and extraordinary association between SOIA and HNPCC, which has never been published before, since SOIA, in this case, could have been developed in the setting of HNPCC syndrome.