Cyst Features and Risk of Malignancy in Intraductal Papillary Mucinous Neoplasms of the Pancreas: A Meta-Analysis

BACKGROUND & AIMS: International guidelines for the management of intraductal papillary mucinous neoplasms (IPMNs) of the pancreas recommend surgical resection of those with specific characteristics. We performed a meta-analysis to evaluate the risk of malignancy associated with each of these features of IPMNs. METHODS: We performed a comprehensive search of MEDLINE from January 1, 1996, to November 11, 2011, for studies that included any of the features mentioned in the consensus guidelines for surgical resection of main duct and branch duct IPMNs. Data were analyzed from 41 studies for the following features: cyst size greater than 3 cm, the presence of mural nodules, dilated main pancreatic duct, symptoms, and main duct vs branch duct IPMNs. Malignant IPMNs were defined as those with carcinoma in situ or more advanced histology. A separate meta-analysis was performed for each risk factor to calculate pooled odds ratios (ORs). A random-effects model was used, based on the assumption of variation among study populations. RESULTS: The risks of malignancy associated with individual cyst features were as follows: cyst size greater than 3 cm (OR, 62.4; 95% confidence interval [CI], 30.8-126.3), presence of a mural nodule (OR, 9.3; 95% CI, 5.3-16.1), dilatation of the main pancreatic duct (OR, 7.27; 95% CI, 3.0-17.4), and main vs branch duct IPMN (OR, 4.7; 95% CI, 3.3-6.9). There was a moderate level of heterogeneity among studies (I-2 range, 34-67). CONCLUSIONS: Based on a meta-analysis, cyst features proposed by the international guidelines for resection of IPMN were highly associated with malignancy. However, based on our findings, not all cyst features should be weighted equally when considering risk of malignancy; cyst size greater than 3 cm was associated most strongly with malignant IPMN.