A 87-year-old female was pointed out wall thickness in the upper part of gastric body for examination of anemia. The mass had a contrast effect, some of it protruded outside the wall, and the surrounding lymph nodes were enlarged. Upper endoscopy showed irregular ulcerative lesion with submucosal volume from posterior wall to the greater curvature in the upper part of gastric body. Biopsy was performed, and GIST of stomach was diagnosed. Surgery was performed for the GIST of the stomach. During open surgery, invasion of pancreatic tail was observed, therefore proximal gastrectomy with D1 lymph node dissection and distal pancreatectomy were performed. Pathologically, the tumor measured 95×78×65 mm with mitotic figures(38/50 high-power fields). Immunohistochemical analysis revealed that tumor cells expressed positive results for c-kit, α-SMA and CD34, and negative results for S-100 and desmin on the basis of the histology and immunostaining profile, the tumor was diagnosed as a GIST. The patient was classed as high risk according to Fletcher's risk classification. Tumor invades pancreatic tail, and lymph node metastasis was observed. She was discharged on the postoperative day 27 and alive without tumor recurrence at 6 months after surgery, not undergoing adjuvant chemotherapy.