Collision tumor of the stomach: a case of an adenocarcinoma and a gastrointestinal stromal tumor

A collision tumor of the stomach is a rare event. We report the case of a collision tumor of the stomach consisting of an adenocarcinoma and a gastrointestinal stromal tumor (GIST). This is, to our knowledge, the second report in the literature of such a case. A 71-year-old man with abdominal discomfort underwent an esophagogastroduodenoscopy which revealed a tumor of the oesophagogastric junction. A total gastrectomy was performed. Histologic examination showed a mixed tumor consisting of a primary adenocarcinoma and multiple nodules of GIST. The adenocarcinoma showed both diffuse and intestinal growth, angio-invasion and metastasis to lymph nodes. The GIST tumor cells were strongly immunoreactive to CD117 and CD34. Based on mitotic index, size and cytonuclear details, the biological behavior of this GIST tumor was supposed to be benign. This case reports the rare finding of a collision tumor consisting of an adenocarcinoma and a GIST with an unknown etiology.