Main Pancreatic Duct Intraductal Papillary Mucinous Neoplasms: Accuracy of MR Imaging in Differentiation between Benign and Malignant Tumors Compared with Histopathologic Analysis

Purpose: To retrospectively determine the accuracy of magnetic resonance (MR) imaging combined with MR cholangiopancreatography (CP) in differentiating benign from malignant intraductal papillary mucinous neoplasms (IPMNs) involving the main pancreatic duct (MPD), with histopathologic analysis as the reference standard. Materials and Methods: The informed consent requirement was waived for this institutional review board-approved study. A total of 51 patients with histopathologically proved IPMNs (MPD IPMN, n = 29; mixed type IPMN, n = 22), underwent MR imaging, MR CP, and surgery, with a mean interval of 2.6 months between MR examination and surgery. Qualitative image analysis included assessment of the site of MPD dilatation (head of the pancreas, body and/or tail of the pancreas, or diffuse), presence or absence of duct wall nodules, and contrast enhancement of the MPD walls. Quantitative image analysis included measurement of the maximum diameter of the MPD. A comparison of adenomas and borderline IPMNs with cancerous IPMNs was performed with the Student t test or the Mann-Whitney U test for continuous variables. Results: At histopathologic analysis, 27 IPMNs were classified as carcinomas; 13, as borderline tumors; and 11, as adenomas. MPD wall nodules were observed in 16 carcinomas involving the MPD and one adenoma or borderline neoplasm (P < .00001). Duct wall enhancement was observed in 20 MPD or mixed type carcinomas and five adenomas or borderline neoplasms (P < .0001). The median maximal diameter of the MPD was 18 mm in malignant MPD or mixed type IPMNs and 11 mm in benign borderline IPMNs (P = .038). No significant difference in the overall 5-year survival rate of patients with MPD IPMNs and those with mixed type IPMNs was observed (P = .813). Conclusion: Duct wall nodules and enhancement of the MPD walls are signs of malignant MPD or mixed type IPMNs. (C) RSNA, 2009