Laterally Spreading Adenocarcinoma Involving the Lower Bile Duct and Duodenum Expressing Heterogeneous Immunohistochemical Phenotypes.

A 70-year-old man was admitted to our hospital due to elevated levels of hepatobiliary and pancreatic enzymes. Computed tomography showed contrast-enhanced mucosal hypertrophy from the duodenal papilla to the distal bile duct. Endoscopic examinations revealed a laterally spreading granular tumor and ampullary swelling. After surgical resection, an examination revealed well-differentiated adenocarcinoma of the ampulla with tubular adenoma spreading from the distal common bile duct to the second part of the duodenum showing both bile duct and duodenal phenotypes. To our knowledge, this is the first case of a tumor spreading from the bile duct to the duodenum that exhibited multiple phenotypes.