Pancreatic duct (PD) obstructed in only ∼ 50%, and usually does not cause upstream pancreatic atrophy
Small masses often not visualized on CT
– Secondary signs should suggest presence of tumor (e.g., double duct sign, etc.)
• MR: Low signal on T1WI, intermediate signal on T2WI, and hypoenhancing on T1WI C+
Diffusion-weighted images may increase sensitivity for small masses
TOP DIFFERENTIAL DIAGNOSES
• Pancreatic head adenocarcinoma involving ampulla
• Ampullary adenoma
• Distal CBD cholangiocarcinoma
• Periampullary duodenal carcinoma
• Ampullary carcinoid tumor
PATHOLOGY
• Markedly increased incidence in hereditary polyposis syndromes
• Lesions can be divided into 3 forms
Tumors arising from duodenal epithelium (intestinal type): Prognosis comparable to duodenal carcinoma
Tumors arising from pancreaticobiliary epithelium of distal CBD/PD (pancreaticobiliary type): Worst prognosis, with outcomes similar to pancreatic adenocarcinoma
Intraampullary tumors: Best prognosis with early ductal obstruction and consequent early presentation
CLINICAL ISSUES
• Obstructive jaundice (80%) most common symptom
• Same surgical treatment (Whipple procedure) as for all periampullary neoplasms
(Left) Graphic shows ampullary carcinoma causing obstruction of both the common bile duct (CBD) and the pancreatic duct (PD) .
(Right) ERCP in a patient with a history of familial polyposis shows a small mass causing obstruction of the distal common duct at the ampulla. Patients with familial polyposis have a substantially increased risk of developing ampullary (and other) carcinomas. Lifelong surveillance is required to detect bowel, stomach, and biliary tumors.
(Left) Coronal CECT demonstrates a classic double-duct sign caused by an ampullary carcinoma , with obstruction of both the common bile duct and pancreatic duct . Note the abrupt occlusion of both ducts by the mass.
(Right) Coronal CECT demonstrates a lobulated mass centered at the ampulla obstructing the pancreatic and common bile ducts. While this was a pancreaticobiliary type lesion at histology, individual subtypes of ampullary carcinoma cannot be distinguished on imaging.
TERMINOLOGY
Definitions
• Heterogeneous group of malignant epithelial neoplasms (adenocarcinoma) arising from ampulla of Vater
IMAGING
General Features
• Best diagnostic clue
Soft tissue mass centered in ampulla
Double duct sign with obstruction of both common bile duct (CBD) and pancreatic duct (PD)
• Location
Centered in region of ampulla of Vater or overlying periampullary duodenal mucosa
• Size
1-4 cm in diameter; mean 2.7 cm
• Morphology
Can be either well-defined lobulated mass or more infiltrative and ill defined
CT Findings
• Mass with variable attenuation (most often hypodense) centered in ampulla
Can be well defined/lobulated or poorly marginated/infiltrative
Almost always obstructs CBD with abrupt cut-off of CBD by mass
PD obstructed in only ∼ 50% of cases, with ampullary tumors much less likely than pancreatic cancer to cause upstream pancreatic atrophy
• Small masses may not be visualized on CT (or any other radiological imaging modality)