Introduction Both gastric choriocarcinoma and small cell carcinoma are extremely rare, both accounting for approximately 0.1% of all gastric cancers. Therefore, simultaneous occurrence of gastric choriocarcinoma and small cell carcinoma is even rarer. Presentation of case An 84-year-old Japanese man was referred to our hospital with the chief complaint of dysphagia. Laboratory data showed iron deficiency anemia. Contrast-enhanced computed tomography of the abdomen revealed thickened wall of the stomach at the fundus and several enlarged abdominal lymph nodes. Upper gastrointestinal endoscopy showed a friable gastric tumor with necrosis in the gastric cardia extending to the abdominal esophagus. Small cell carcinoma was diagnosed based on pathological examination of biopsy specimens. The anemia, which was probably because of tumor bleeding, progressed despite repeated transfusion
therefore, a semi-urgent laparotomy was performed to control hemorrhage. Finally, total gastrectomy and lymph node resection were performed. Based on pathological findings, a diagnosis of collision tumor of choriocarcinoma and small cell carcinoma of the stomach was confirmed. Discussion When encountering large tumors with necrosis or hemorrhage in the stomach, the possibility of choriocarcinoma component should be considered. Moreover, when small cell carcinoma is morphologically suspected, even if slightly, additional immunohistochemical staining must be performed. Conclusion This report detailed an extremely rare case of collision tumor of choriocarcinoma and small cell carcinoma of the stomach.