A case of collision of tubular adenocarcinoma of pancreas and signet ring cell carcinoma of middle and lower bile duct

A 77-years-old man admitted for jaundice and white stool was diagnosed with a middle and lower bile duct or pancreas head cancer, necessitating subgastric preserving pancreaticoduodenectomy with lymph node dissection. Resected material showed two tumors in the middle and lower bile duct and pancreas head. Histopathologically, signet ring cell carcinoma of the middle and lower bile duct had infiltrated the pancreas severely, and well-differentiated tubular adenocarcinoma was found in the pancreas head. We diagnosed this as a collision of two cancers because no cell transference was found between the two tumors. The patient underwent adjuvant chemotherapy using gemcitabine and remains alive with no evidence of reccurrence 14 months after surgery. Collision cancer of the pancreas showed features of both middle∼lower bile duct and pancreas head cancer in preoperative imaging, making the diagnosis very difficult.