Ampullary adenoma is a benign neoplasm arising from the ampulla of Vater and is the precursor lesion of ampullary adenocarcinoma (adenoma-carcinoma sequence). It may be sporadic or familial adenomatous polyposis (FAP)-associated — ampullary adenoma prevalence is 50-90% in FAP patients. Usually asymptomatic and incidentally detected; large adenomas may develop intermittent jaundice or pancreatitis. Endoscopic papillectomy is curative for small adenomas (<2 cm, no high-grade dysplasia). Malignant transformation risk increases with size and villous component — adenomas >2 cm or with villous histology have 30-40% malignancy risk.
Age Range
40-75
Peak Age
55
Gender
Equal
Prevalence
Rare
Ampullary adenoma is a benign neoplastic proliferation arising from intestinal or pancreatobiliary-type mucosal epithelium at the ampulla of Vater. In sporadic cases, APC gene mutation or beta-catenin pathway activation plays a role; in FAP, APC germline mutation triggers ampullary adenoma development. The adenoma-carcinoma sequence parallels the mechanism in colorectal cancer — normal epithelium → adenoma (low-grade dysplasia) → high-grade dysplasia → invasive carcinoma. Histologically, it may be tubular, villous, or tubulovillous type — malignant transformation risk increases as villous component increases. In imaging, small ampullary adenomas are usually not visualizable; large adenomas enhance as polypoid mass at the ampulla and may cause mild biliary/pancreatic duct dilatation. Papillary growth pattern of adenoma creates protrusion into duodenal lumen — pathognomonic at endoscopy.
Small, homogeneously enhancing polypoid lesion at ampullary region — without invasion findings and significant duct dilatation. Endoscopic evaluation and biopsy are mandatory for diagnosis.
Small (<2 cm), homogeneously enhancing polypoid lesion in ampullary region on portal venous phase. Lesion may protrude into duodenal lumen. Mild dilatation of CBD and pancreatic duct may accompany but prominent double duct sign is not expected. Periampullary fat planes are preserved — no invasion findings. Pancreatic head is normal size and structure.
Report Sentence
Small homogeneously enhancing polypoid lesion at ampullary region is noted, which may be consistent with ampullary adenoma; endoscopic evaluation is recommended.
Polypoid lesion with intermediate signal intensity in ampullary region on T2-weighted images. MRCP may show mild dilatation at lower end of CBD and pancreatic duct — but abrupt termination (meniscus sign) is usually not prominent. In villous adenomas, papillary surface structure may create more heterogeneous appearance on T2. No perilesional edema or invasion findings.
Report Sentence
Polypoid lesion with intermediate signal intensity at ampullary region on T2-weighted series is noted.
Mild CBD dilatation (6-8 mm) detected on US but no stone visualized within CBD. Ampullary region cannot usually be directly evaluated due to duodenal gas. Gallbladder is normal or mildly distended. Minimal intrahepatic bile duct dilatation may accompany. Pancreatic duct dilatation is difficult to demonstrate on transabdominal US.
Report Sentence
Mild CBD dilatation without stone is noted; ampullary region should be evaluated with CT/MR or EUS.
Mucosal enhancement at ampullary region on arterial phase — reflecting adenoma neovascularization. Normal ampullary mucosa may also enhance in arterial phase but enhancement is more prominent in adenoma with accompanying focal thickening/polypoid protrusion. On CT with oral contrast, filling defect at ampulla may be detected within contrast in duodenal lumen. Water oral contrast (negative oral contrast) protocol improves detection of ampullary lesions.
Report Sentence
Focal mucosal enhancement and mild polypoid thickening at ampullary region on arterial phase is noted.
Ampullary adenoma shows mild or no diffusion restriction on DWI — ADC values are significantly higher than adenocarcinoma (usually >1.4 × 10⁻³ mm²/s). This difference is the most useful MR parameter for malignant-benign differentiation. Large villous adenomas may show mild diffusion restriction — in this case, high-grade dysplasia or focal carcinoma component should be considered.
Report Sentence
No significant diffusion restriction in ampullary lesion on DWI with ADC values consistent with benign adenoma.
Criteria
Tubular glandular structure >75%; lowest malignancy risk
Distinct Features
Homogeneous enhancement, smooth surface, small size
Criteria
Villous component >75%; highest malignancy risk (30-40%)
Distinct Features
Papillary surface, larger size, mildly heterogeneous enhancement
Criteria
Tubular and villous component 25-75% each; intermediate malignancy risk
Distinct Features
Mixed enhancement pattern, intermediate size
Distinguishing Feature
Adenocarcinoma forms larger, heterogeneously enhancing mass with invasion findings + prominent diffusion restriction on DWI; adenoma is small, homogeneous without invasion findings
Distinguishing Feature
Stone shows echogenic structure + posterior acoustic shadow; adenoma is solid polypoid lesion without acoustic shadow
Distinguishing Feature
Gallbladder polyp is located in gallbladder lumen; ampullary adenoma is located in duodenal lumen at ampulla of Vater
Urgency
routineManagement
surgicalBiopsy
NeededFollow-up
6-monthAmpullary adenoma can be treated with endoscopic papillectomy (<2 cm, low-grade dysplasia). Surgical resection (Whipple) is considered for >2 cm, villous histology, or high-grade dysplasia. Regular screening and prophylactic papillectomy recommended for FAP patients. Recurrence rate after papillectomy is 10-30% — endoscopic follow-up is required.
Ampullary adenoma is a precursor of the adenoma-carcinoma sequence with 30-40% malignant transformation risk, and endoscopic papillectomy with resection is recommended. Systematic papilla screening should be performed in FAP patients. Endoscopic follow-up is required for recurrence after complete resection.