Simultaneous development of adenocarcinoma and gastrointestinal stromal tumor (GIST) in the stomach: case report

BACKGROUND Gastrointestinal stromal tumors (GISTs) and adenocarcinoma are distinct neoplasms originating from different cell layers. Approximately 20% of patients with GIST develop other cancers. CASE PRESENTATION We report a case of the coexistence of adenocarcinoma and gastrointestinal stromal tumor (GIST). Gastric endoscopy showed the ulcerated tumor with bleeding along the lesser curvature of the proximal stomach and a submucosal nodule that measured about 3 cm in diameter in the lower part of the stomach body. Their pathological examination showed gastric cancer (poorly differentiated diffuse adenocarcinoma) and GIST (low-risk category). Further, immunohistochemical staining for C-kit and CD34 was positive, while that for SMA and S-100 was negative. CONCLUSION Although it is not easy to speculate on the coexistence of adenocarcinoma and GIST, pre-and post-operative diagnoses may be essential, and such cancer development is not considered to be unusual.