A 46-year-old woman was admitted to our hospital and was diagnosed with a gastric submucosal tumor at the medical examination. Upper endoscopic examination revealed a submucosal tumor in the lower body of the stomach. Abdominal computed tomography (CT) revealed a large tumor of dimensions 51 × 32 mm in the lower body of the stomach with a mixed appearance: a solid part exhibiting a contrast effect and a cystic part exhibiting no contrast. Endoscopic ultrasonic fine needle aspiration biopsy (EUS-FNAB) was performed, and a gastrointestinal stromal tumor (GIST) was diagnosed by immunohistopathological examination. Laparoscopic surgery with five ports was performed for resection. After securing the safety margin the tumor was resected circumferentially using an ultrasonically activated device (USAD). Resection entailed a significant portion of the gastric wall. During surgery, a support yarn hooked in the minor axis direction, and the defect was closed using an automatic suturing device three times. According to the third edition of the GIST clinical practice guidelines, indications for laparoscopic resection of GISTs over 5cm have been relaxed. It was considered that careful laparoscopic resection would be possible even though this was a large GIST exceeding 5 cm
