We report herein the case of a 70-year-old woman with histologically confirmed gastric Borrmann type 3 cancer in the posterior wall of the fundus in whom computed tomography demonstrated a dilated portal trunk and splenic vein containing a low-density mass, but no evidence of liver metastases. The venous phase of a superior mesenteric arteriogram subsequently showed occlusion of the main portal vein with venous collaterals. At surgery, a tumor thrombus was noted to extend from the short gastric vein to the portal vein via the splenic vein. Thus, an extensive gastric resection together with removal of the tumor thrombus from the veins was performed, and successful results were achieved.