Gastric collision tumor (carcinoid and adenocarcinoma) with gastritis cystica profunda.

We report a rare case of gastric collision tumor (carcinoid and adenocarcinoma) with gastritis cystica profunda that developed in a 49-year-old Japanese man. Early gastric cancer (moderately differentiated tubular adenocarcinoma) was present at the edge of an ulcer in the posterior wall of the upper gastric body. In addition, a carcinoid tumor was found adjacent to adenocarcinoma. This tumor displayed ribbonlike or trabecular patterns, and numerous constituent cells were positive for the argyrophil reaction with Grimelius' stain and serotonin. Electron microscopic features of this tumor confirmed typical carcinoid. There was no merged appearance between both tumors, suggesting collision-type tumor.