Primary small bowel adenocarcinoma with loss of nuclear expression of PMS2 after resection of mucinous cholangiocarcinoma

Abstract Mucinous cholangiocarcinoma is an extremely rare form of intrahepatic cholangiocarcinoma that has been characterized by rapid growth, widespread metastasis and poor prognosis. These tumors have been shown to be a part of the Lynch syndrome tumor spectrum, however, the role of DNA mismatch repair (MMR) deficiency in their development is poorly understood. We present the case of a 74-year-old male with cholangiocarcinoma, who underwent Roux-en-Y hepaticojejunostomy and extended left hepatectomy and was diagnosed with a primary small bowel adenocarcinoma 2 years later. Immunohistochemistry testing for mismatch repair proteins was significant for the loss of nuclear expression of PMS2. Taken together, the cause of both the mucinous cholangiocarcinoma and primary small bowel adenocarcinoma with PMS2 loss in the patient presented here is likely genetic, suggestive of a cancer syndrome.