A collision tumor composed of cancers of the bile duct and ampulla of Vater--immunohistochemical analysis of a rare entity of double cancer.

Collision cancer of the bile duct and the papilla of Vater is an extremely rare entity. This is the first report of a case of bile duct collision cancer. A 75-year-old man presented with jaundice. Computed tomography showed isodensity masses in the middle bile duct and the papilla of Vater. Magnetic resonance cholangiopancreatography showed a tuberous filling defect in the middle bile duct. Gastroduodenal endoscopy showed a tumor with ulceration at the papilla of Vater. The patient was diagnosed with cancers of the middle bile duct and the papilla of Vater, and a pylorus-preserving pancreatoduodenectomy was performed. On pathological examination, the tumor in the middle bile duct showed a well differentiated carcinoma that had spread to the proximal bile duct, whereas the tumor in the papilla of Vater showed a papillo-tubular carcinoma with a marked production of mucin, suggesting an intestinal type of ampullary cancer. These tumors were directly communicated by microscopic findings. Therefore, the immunohistochemical characteristics were analyzed, using several antibodies, to determine whether the origins of the 2 cancers were different or not. As a result, it was concluded that this was a case of collision cancer of the middle bile duct and the papilla of Vater.