A rare collision tumor of gastrointestinal stromal tumor of the stomach and pancreatic ductal adenocarcinoma

Collision tumors involving GIST are very rare. Herein, we report a collision tumor consisting of gastric gastrointestinal stromal tumor (GIST) and pancreatic ductal adenocarcinoma. The patient was a 76-year-old Chinese male, presenting with abdominal distension, haematemesis and melena. Both the CT scan images and the gross appearance demonstrated special features indicating the possibility of a tumor with two different elements, which were once ignored by the initial diagnosticians. Microscopic and immunohistochemical features identified a collision tumor involving GIST and pancreatic ductal adenocarcinoma. To our best, this is the first such a case reported in the English literature.