Background:Gastrointestinal stromal tumors (GISTs) possess inherent malignant potential (1), and management becomes particularly complex when lesions arise at the gastric cardia, where restricted endoscopic maneuverability and proximity to the esophagogastric junction impose significant technical limitations. Advances in third-space endoscopy have expanded therapeutic possibilities, allowing organ-preserving alternatives such as ESD, EFTR, STER, and POET for selected subepithelial tumors (3,4). The 2022 ESGE guideline endorses endoscopic resection as a feasible alternative to surgery for gastric GISTs ≤35 mm in appropriate candidates (2), highlighting the growing relevance of minimally invasive endoscopic approaches.

Case presentation:An 84-year-old man presented with epigastric discomfort. Endoscopy identified a subepithelial lesion at the gastric cardia. CT and EUS revealed a 3.9 × 3.0 cm hypoechoic mass originating from the muscularis propria with exophytic extension into the peritoneal cavity, consistent with a probable GIST. Given his age, elevated surgical risk, and preference for organ preservation, POET was selected following multidisciplinary evaluation.

Procedure:After submucosal injection, a 1.5–2 cm mucosal incision was created in the lower esophagus, and a submucosal tunnel was advanced toward the gastric cardia. The lateral and superior dissection planes were developed first, enabling stable visualization in this anatomically constrained region. The lesion demonstrated a prominent exophytic component with firm adhesions to the anterior abdominal wall and the inferior aspect of the left hepatic lobe, which were carefully released under direct endoscopic control. Complete mobilization allowed en bloc retrieval through the tunnel. A controlled full-thickness defect created during resection was closed internally using endoclips along the lesser curvature at the corresponding projection, achieving secure closure and avoiding surgical conversion.

Outcome:Histopathology confirmed a 3.5 × 2.9 cm CD34-positive intermediate-risk GIST. Recovery was uneventful: oral intake resumed within 24 hours, and discharge occurred on postoperative day 3. At three-month follow-up, endoscopy demonstrated complete mucosal healing with no recurrence.

Conclusion:This case demonstrates the feasibility, safety, and organ-preserving value of POET for anatomically challenging gastric cardia GISTs in elderly or high-risk surgical patients. It underscores the expanding role of third-space endoscopy in providing curative minimally invasive therapy for upper gastrointestinal subepithelial tumors.