Differential Features of Pancreatobiliary- and Intestinal-type Ampullary Carcinomas at MR Imaging

Abstract

To define the differential imaging features of pancreatobiliary- and intestinal-type ampullary carcinomas at magnetic resonance (MR) imaging and to correlate these features with pathologic findings. This retrospective study was approved by the institutional review board; informed consent was waived. Fifty patients with surgically confirmed ampullary carcinoma and preoperative MR results were included. Two radiologists, blinded to histologic type of cancer, evaluated imaging findings in consensus. Univariate and multiple logistic regression analysis were performed to define imaging findings that were useful for differentiation of the two types of carcinomas. On the basis of hematoxylin-eosin and immunohistochemical staining, 35 patients were classified as having pancreatobiliary type; and 15 patients, intestinal type. At MR, all of 15 intestinal carcinomas were nodular, whereas 16 (46%) of 35 pancreatobiliary carcinomas were infiltrative. Intestinal carcinomas were isointense (13 [87%] of 15) to hyperintense (two [13%] of 15), whereas 34% (12 of 35) of pancreatobiliary carcinomas manifested as hypointense compared with the duodenum on T2-weighted MR images (P = .034). Intestinal carcinoma commonly manifested with an oval filling defect at the distal end of the bile duct on MR cholangiopancreatographic (MRCP) images (11 [73%] of 15 vs four [11%] of 35 in pancreatobiliary type) (P < .001). At endoscopy, intestinal carcinoma manifested with an extramural protruding mass (n = 15, 100%) with a papillary surface (n = 11, 73%), whereas pancreatobiliary carcinoma manifested with intramural protruding (n = 5, 28%) or ulcerating (n = 1, 6%) gross morphologic features (P = .047) with a nonpapillary surface (n = 17, 94%) (P < .001). Multiple logistic regression analysis showed that an oval filling defect at the distal end of the bile duct was the only independent finding for differentiating intestinal from pancreatobiliary carcinoma (P = .027). An oval filling defect at the distal end of the bile duct on MRCP images and an extramural protruding appearance with a papillary surface at endoscopy are likely to suggest intestinal ampullary carcinoma.