MR cholangiopancreatographic differentiation of benign and malignant intraductal mucin-producing tumors of the pancreas

OBJECTIVE, The purpose of this study was to establish MR cholangiopancreato graphic criteria for discriminating benign from malignant intraductal mucin -producing tumors of the pancreas. MATERIALS AND METHODS, Thirty-one patients with 34 intraductal mucin-produc ing tumors underwent MR cholangiopancreatography. Tumors were classified as either main duct type (n = 10) or branch duct type (n = 24). In patients w ith the main duct type, the maximum diameter and the location of the main p ancreatic duct, the extent of main pancreatic duct dilatation, and the pres ence of a filling defect were evaluated. For branch duct type, the location and maximum diameter of the cystic lesion, the presence of a filling defec t, and the presence of associated main pancreatic duct dilatation were eval uated. RESULTS. In patients with the main duct type, the main pancreatic duct was significantly narrower when associated with benign rather than malignant tu mors. All malignant tumors showed diffuse main pancreatic duct dilatation, whereas arl benign tumors showed segmental dilatation. Among patients with branch duct type, the cyst was smaller when it was a benign rather than mal ignant tumor. All but one malignant tumor showed mild associated main pancr eatic duct dilatation, whereas benign tumors were not associated with main pancreatic duct dilatation. Filling defects suggested malignancy, although half of the malignant tumors had no filling defects. CONCLUSION. In patients with intraductal mucin-producing tumors of the panc reas, tilling defects are indicative of malignancy. Diffuse main pancreatic duct dilatation greater than 15 mm (main duct type), or any main pancreati c duct dilatation (branch duct type), is strongly associated with malignanc y.