A Case Study of a Gastric Collision Tumor with an Adenocarcinoma and a Carcinoid Tumor.

Adenocarcinoma is the most common malignant gastric neoplasm, contrary to a gastric carcinoid which is relatively uncommon. The occurrence of an adenocarcinoma and a typical carcinoid tumor is rare and are morphologically classified into two subgroups. The first type is a composite- type tumor, which is characterized as a randomly assorted adenocarcinoma and a typical carcinoid tumor. The second type is a collision-type tumor, which is a double tumor with a “side by side” or “overlay” pattern. To the best of our knowledge, only 2 cases of the collision type tumors have been reported in the Korean literature. We have encountered a collision tumor which occurred in the antrum of the stomach and which invaded the regional lymph nodes by means of a highly malignant gastric carcinoid. The following report is a description of the collision tumor case as well as a literature review. (Korean J Gastrointest Endosc 2008;36:159-164)