Pathologic Subtypes of Ampullary Adenocarcinoma: Value of Ampullary MDCT for Noninvasive Preoperative Differentiation.

Abstract

The purpose of this study was to evaluate the utility of ampullary MDCT in the noninvasive, preoperative differentiation of pancreatobiliary and intestinal subtypes of ampullary adenocarcinoma. This retrospective study included 32 patients (20 men, 12 women; age range, 41-81 years) with resected ampullary adenocarcinoma who underwent preoperative contrast-enhanced ampullary MDCT. Two radiologists, blinded to pathologic diagnosis of adenocarcinoma subtype, evaluated the presence of seven MDCT features independently. MDCT findings and ampullary adenocarcinoma subtypes were correlated using chi-square and Fisher exact tests. Interobserver agreement was evaluated using the Cohen kappa statistic. When evaluated with ampullary MDCT, the intestinal and pancreatobiliary subtypes were significantly different in terms of lesion morphology (p < 0.0001), papillary shape (p < 0.0001), common bile duct (CBD) infiltration and dilatation (p = 0.003 and p = 0.0004, respectively), duodenopancreatic groove infiltration (p = 0.0009), and pancreaticoduodenal artery involvement (p = 0.004). Pancreatobiliary subtype tumors were more often infiltrative in morphology (18/18) and showed retracted papilla (14/18), CBD (18/18) and main pancreatic duct (MPD) infiltration (12/18), dilated CBD (18/18) and MPD (13/18), fixed duodenopancreatic groove appearance (15/18), and pancreaticoduodenal artery involvement (12/18). Intestinal subtype carcinomas were more frequently nodular (14/14) and had a bulging papilla (13/14), a free duodenopancreatic groove appearance (11/14), and no pancreaticoduodenal artery involvement (2/14). When all features were taken into account, MDCT showed sensitivity of 85.7% and specificity of 83.3% in differentiating intestinal and pancreatobiliary subtype tumors. Accuracy, positive predictive value, and negative predictive value of MDCT were 84.4%, 80%, and 88.2%, respectively. Interobserver agreement was almost perfect for the presence of each imaging feature (κ > 0.8). Ampullary MDCT can be useful to differentiate pancreatobiliary and intestinal subtypes of ampullary adenocarcinoma preoperatively, provided the duodenum is optimally distended at imaging.