Preoperative histological subtype classification of intraductal papillary mucinous neoplasms (IPMN) by pancreatic juice cytology with MUC stain

Abstract

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 cholangiopancreatography. 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.