Submucosal Tunnel Endoscopic Resection of a Gastric Schwannoma Mimicking a Submucosal Tumor

Gastric schwannomas are rare benign mesenchymal tumors originating from Schwann cells of the myenteric plexus, accounting for less than 0.2% of all gastric neoplasms. They are often asymptomatic but may present with abdominal pain, bleeding, or obstructive symptoms when large. Endoscopic ultrasound is crucial for preoperative evaluation, while definitive diagnosis relies on histopathology and immunohistochemistry, typically showing strong S-100 protein positivity and negativity for CD117, DOG-1, and smooth muscle actin. Traditional management for symptomatic or large lesions has been surgical resection. However, submucosal tunnel endoscopic resection has emerged as a promising minimally invasive alternative. A case of a 73-year-old female with recurrent abdominal distension is presented, in whom esophagogastroduodenoscopy identified an 8.2 mm submucosal tumor in the gastric body, and endoscopic ultrasound confirmed origin from the muscularis propria. The patient underwent submucosal tunnel endoscopic resection, which involved creating a submucosal tunnel to access and resect the tumor while preserving the overlying mucosa. The procedure was completed successfully without perforation or significant bleeding. Histopathological and immunohistochemical examination confirmed a benign schwannoma with S-100 positive and CD117 and DOG-1 negative staining. The patient was discharged on postoperative day 6 without complications. At 14-month follow-up, no recurrence was observed. This case demonstrates the feasibility and safety of STER in a carefully selected patient with a gastric schwannoma, with minimal mucosal injury and no postoperative complications.