Gastric collision tumor composed of early-stage gastric carcinoma and gastrointestinal stromal tumor: a case report.

Collision tumors composed of adenocarcinoma and gastrointestinal stromal tumor (GIST) of the stomach are extremely uncommon, and only a few cases have been reported in the English literature. In the present case, a 67-year-old woman visited a local hospital for vomiting and hematemesis. An esophagogastroduodenoscopy study indicated an elevated lesion with ulceration. Histology of the endoscopic biopsy specimen indicated gastric adenocarcinoma. The patient underwent laparoscopic distal gastrectomy with D2 lymph node dissection. The resected specimen showed that the primary tumor consisted of a GIST and that early-stage gastric carcinoma coexisted in the mucosa surrounding the central ulceration of the GIST. Although close contact of the adenocarcinoma and GIST was observed on the mucosal surface, no intermixing of tumor cells was observed in the primary tumor. This case is an extremely rare case of a collision tumor composed of early-stage gastric adenocarcinoma and GIST occurring in the stomach, which provides some insight into a better understanding of the pathogenesis of collision tumors.