Abstract
A 64-year-old man visited the emergency clinic in our hospital complaining of epigastric pain and melena. A type 3 gastric tumor was found in the posterior wall of the middle part of the stomach in the upper gastrointestinal endoscopy, and was diagnosed as poorly differentiated adenocarcinoma by a biopsy. We immediately performed endoscopic hemostasis followed by total gastrectomy. The resected specimen revealed an ulcerative lesion having two different centers in the posterior wall of the middle body. Histopathology identified poorly differentiated adenocarcinoma and neuroendocrine carcinoma in the same tumor lesion. Since there were no mixed or transitional area between two cancers, collision cancer was diagnosed. Collision cancer has a clear boundary though it has not transitional lesion. This case also has diffuse submucosal heterotopic gastric glands, which are comparatively rare.
There have been no reports on collision cancer composed of gastric adenocarcinoma and neuroendocrine carcinoma so far, and our case is extremely rare.
