Acute Pancreatitis is a Predictive Factor for Malignancy in Mixed or Main Duct Intraductal Papillary Mucinous Neoplasms

Objectives: It is still unclear whether acute pancreatitis (AP) is a predictor of malignancy. Using patients enrolled from a single institution, the objective of this study was to determine whether AP as a complication of intraductal papillary mucinous neoplasm (IPMN) predicts malignancy, and to clarify the clinicopathological characteristics of IPMN with AP. Methods: The clinicopathological features of 87 patients who underwent surgical resection for IPMN between October 1998 and May 2010 were investigated. In this study, malignancy was defined as high-grade dysplasia (noninvasive carcinoma) and invasive carcinoma. Macroscopic classification was based on the 2012 international consensus guidelines and IPMN with a main pancreatic duct size of >5 mm was classified as either mixed or main duct IPMN. Results: Among the patients, who underwent surgical resection for IPMN, AP was present in 18% (16/87) and malignancy was present in 43% (37/87). The median period from the first AP episode until surgery was 5.5 months (range: 1.0-116.3 months). There was no significant difference in the frequency of malignancy between IPMN patients with and without AP [63% (10/16) vs. 38% (27/71); p=0.096]. In mixed or main duct IPMN, malignancy was more frequent in patients with AP than in those without AP [91% (10/11) vs. 48% (22/46); P=0.016]. Comparison of the clinicopathological features between malignant IPMN with and without AP showed that the frequency of highgrade dysplasia (non-invasive carcinoma) was significantly higher in the former [80% (8/10) vs. 37% (10/27); P=0.029]. Conclusions: AP itself may not be a predictive factor for malignancy in IPMN, but may be such a predictor in mixed or main duct IPMN. AP is also an important clinical sign that must not be overlooked, as it may indicate the presence of malignant lesions at an earlier stage.