Ampullary tumors are centered in the Ampulla of Vater and originate from the intestinal-type mucosa. The benign end of the spectrum includes villous adenoma (shown here) and villoglandular polyp. The malignant forms include adenocarcinomas (in-situ or invasive) that usually arise in the setting of a preexisting benign tumor. In this image, the lower third shows normal duodenal mucosa. The upper two-thirds shows villous adenoma with varying degrees of dysplasia; some areas have high-grade dysplasia (carcinoma-in-situ).