Infiltrating poorly-differentiated adenocarcinoma arising in the ampullary region. The lesion was present at the base of a villous adenoma which had typical well-differentiated morphologic features. Ampullary carcinomas may sometimes show specific morphologic patterns, including a prominent Paneth cell component, hepatoid features, and neuroendocrine differentiation. Immunohistochemically, ampullary carcinomas with intestinal morphology are CK7-ve, CK20+, CDX2+, MUC2+, and p53+. In contrast, they are less likely to show KRAS mutations or loss of DPC4 expression when compared to pancreatic ductal adenocarcinomas.