Preoperative Histological Subtype Classification of Intraductal Papillary Mucinous Neoplasms (IPMN) by Pancreatic Juice Cytology With MUC Stain

Objective: To prospectively evaluate the diagnostic value of preoperative histological subtyping of intraductal papillary mucinous neoplasms (IPMNs) by pancreatic juice cytology (PJC) with mucin (MUC) stain. Background: IPMNs are classified into four subtypes based on their histomorphology and mucin phenotype, and varied degrees of malignant nature and prognosis among these subtypes have been shown. Methods: The subjects were 36 patients with surgically confirmed IPMNs, who underwent PJC preoperatively by endoscopic retrograde cholangiopan-creatography. Histological subtyping of cytological samples with or without MUC stain (MUC1, MUC2, and MUC5AC) was compared with that of resected specimens. Results: Histologically, low-grade dysplasia was found in 4 patients, intermediate in 10, high grade in 11, and invasive carcinoma in 11. Gastric, intestinal, pancreatobiliary, and oncocytic subtypes corresponded to 16, 14, 5, and 1 patient, respectively. The rate of high-grade dysplasia (HGD) and/or invasive IPMNs was 25% for gastric subtype, 85.7% for intestinal subtype, and 100% for both pancreatobiliary and oncocytic subtypes, showing a significant correlation between histological subtype and rate of HGD and/or invasive IPMN (P < 0.01 for gastric vs nongastric). Histological subtype was successfully diagnosed by PJC in 42% (15/36) without MUC stain, and the rate was significantly improved to 89% (32/36) with MUC stain (P < 0.01). The sensitivity, specificity, and overall accuracy of PJC with MUC stain were 86%, 100%, and 94% for intestinal subtype, respectively. When cytological grade was combined with MUC stain, the diagnosis of HGD/invasive IPMN showed 77.2% sensitivity, 85.7% specificity, and 80.5% accuracy. Conclusions: Preoperative PJC with MUC stain proved to be highly reliable for identifying the histological subtype of IPMN and may provide useful information for deciding surgical indication.