Pancreatic intraductal papillary mucinous neoplasm in a patient with Lynch syndrome

Abstract

Intraductal papillary mucinous neoplasm (IPMN) is a mucin-producing epithelial neoplasm that carries a risk of progression to invasive pancreatic ductal adenocarcinoma. Lynch syndrome is an autosomal dominant condition caused by germline mutations in mismatch repair genes such as MSH2 that lead to microsatellite instability and increased risk of tumor formation. Although families with Lynch syndrome have an increased risk of pancreatic cancer, a clear connection between Lynch syndrome and IPMN has not been drawn. We present a report of a 58 year-old Caucasian woman with multiple cancers and a germline mutation of MSH2 consistent with Lynch syndrome. A screening abdominal computed tomography scan revealed a dilated main pancreatic duct and cystic ductular structure in the uncinate process that were consistent with IPMN of the main pancreatic duct on excision. Immunohistochemistry and polymerase chain reaction of the patient's pancreas specimen did not reveal microsatellite instability or mismatch repair gene loss of expression or function. Our findings may be explained by the fact that loss of mismatch repair function and microsatellite instability is a late event in neoplastic transformation. Given the relative rarity of main duct IPMN, its appearance in the setting of somatic MSH2 mutation suggests that IPMN may fit into the constellation of Lynch syndrome related malignancies.

Keywords: Hereditary nonpolyposis colorectal cancer; Intraductal papillary mucinous neoplasm; Lynch syndrome; MSH2; Microsatellite instability; Pancreatic cancer.

Figure 1

Pancreatic imaging. A: Computed tomography imaging demonstrated progressive dilation of main pancreatic duct as compared to the prior year (white arrow). B: Magnetic resonance cholangiopancreatography shows pancreatic ductal dilation with a normal biliary tree (short white arrow). There is evidence of side-branch dilation within the head and uncinate process (long white arrow).

Figure 2

Surgical anatomy. A: Anatomy after pancreatectomy; B: Grossly normal total pancreatectomy specimen.

Figure 3

Pancreatic duct histology. A: IPMN involving the main pancreatic duct (40 × magnification); B: Neoplastic cells show hyperchromatic nuclei with abundant intracytoplasmic mucin. No high-grade dysplastic cells are present (100 × magnification).

Figure 4

Immunohistochemical staining. Staining for MLH1, PMS2, MSH2, and MSH6 did not reveal loss of mismatch repair protein expression, as the neoplastic cells show uniform nuclear stain (black arrows) for all four markers (40 × magnification).