Mesothelin expression in pancreatic mucinous cysts.

Abstract

Mesothelin (MSLN) is a differentiation antigen found to be overexpressed in intraductal papillary mucinous neoplasms (IPMNs) and is a potential treatment target in pancreatic ductal adenocarcinoma. From institutional archives, 114 cases of resected pancreatic mucinous cysts were identified, including IPMN and mucinous cystic neoplasm (MCN). Immunohistochemical analysis of MSLN was performed on representative sections. MSLN was seen more frequently in neoplastic epithelial cells from IPMN (39/52; P < .0005) and MCN (9/14; P < .0001) compared with unremarkable adjacent pancreatic and bile ducts (0/57) and benign foveolar and duodenal epithelium (0/21). When present, MSLN was diffusely expressed in neoplastic epithelium and only focally expressed in adjacent ducts (8/57). No significant difference was seen (P = .26) in MLSN expression between IPMN (79%) and MCN (83%) when only presence or absence was considered. Our findings suggest that MLSN can be used as a marker of neoplastic transformation of epithelial cells in pancreatic mucinous cysts. The findings can help identify neoplastic mucinous epithelium.