[1766] Mesothelin Expression in Pancreatic Mucinous Cysts

Renee Frank, Nuzhat A Ahmad, Pari Shah, Antonia R Sepulveda, Nirag C Jhala. Hospital of the University of Pennsylvania, Philadelphia, PA; Columbia University, New York, NY

Background: Mesothelin (MSLN) is a differentiation antigen found to be overexpressed and a potential treatment target in pancreatic ductal adenocarcinomas. There is little to no MLSN expression in normal pancreas or chronic pancreatitis and MSLN is not detected in gastric or duodenal epithelium. The expression of MSLN in pancreatic neoplastic mucinous cysts is largely not investigated. The aim of this study was to determine the frequency of MSLN expression in neoplastic epithelium of mucinous pancreatic cysts.
Design: Fifty-four well-characterized cases of pancreatic neoplastic mucinous cysts were identified in our institutional pathology archive (2008-2011) including intraductal papillary mucinous neoplasm (IPMN) and mucinous cyst adenoma (MCN). Immunohistochemical analysis of MSLN was performed on a representative formalin-fixed paraffin embedded sections from each case using standard immunohistochemical protocols. MSLN expression was considered positive with either membranous or cytoplasmic staining and was recorded semiquantitatively in mucinous cysts, adjacent pancreatic ducts and bile duct, and duodenal and gastric foveolar epithelium as follows: 1+ (1- 25% positive cells), 2+ (26-75% positive cells) as and 3+ (>76% positive cells). A 2-tailed Fisher's exact test was used to determine statistical significance.
Results: MSLN expression was noted in the epithelial cytoplasm as well as on the cell surface. MSLN expression was seen more frequently in neoplastic epithelial cells from IPMN (33/41; p< 0.0001) and MCN (8/13; p < 0.0005) in comparison to expression in unremarkable adjacent pancreatic and bile ducts (8/58). When present, MSLN expression was only focally and weakly expressed in unremarkable pancreatic and bile ducts. There was no significant difference (p = 0.26) in MLSN expression between IPMN (81%) and MCN (62%). MSLN expression >2+ was significantly more frequent in IPMN (27/41) than in MCN (3/13), p = 0.01. No MSLN expression was seen in duodenal or gastric foveolar epithelium.
Conclusions: Our findings suggest that MLSN expression can be used as a marker of neoplastic transformation of epithelial cells in pancreatic mucinous cysts. While the biologic significance of MSLN in these neoplasms remains unclear, the findings could help distinguish neoplastic mucinous epithelium from gastrointestinal tract contamination on endosonography guided fine needle aspiration samples from pancreatic cysts.
Category: Pancreas

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 269, Monday Morning


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