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

OBJECTIVE: 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.

MATERIALS AND METHODS: 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.

RESULTS: 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).

CONCLUSION: Ampullary MDCT can be useful to differentiate pancreatobiliary and intestinal subtypes of ampullary adenocarcinoma preoperatively, provided the duodenum is optimally distended at imaging.