Endoscopic submucosal dissection (ESD) of subepithelial lesions (SELs) remains technically demanding, particularly for larger lesions arising in anatomically challenging locations such as the upper gastric body or fundus.The anatomical configuration of the upper stomach often results in unstable endoscope positioning, perpendicular access, and limited tip control and visualization of the dissection plane. These factors increase the risk of incomplete resection, muscular injury, or perforation, and may require surgical conversion, particularly for the excavation technique required for resection of subepithelial lesions arising from the muscularis propria. A method to improve scope stability and control during ESD in thislocation is therefore needed.

We report a stabilization-assisted ESD technique using a rigidizing overtube (Pathfinder®, Neptune Medical, USA) to facilitate complete en bloc resection of a gastric GIST arising from the muscularis propria.Although this device has primarily been described for use in colorectal endoscopic resections, to our knowledge no published reports have documented its application in upper gastrointestinal ESD, making this its first reported use in this anatomical context.The device, which transitions from flexible to rigid through a vacuum-controlled system, was used to stabilize the endoscope shaft and maintain a fixed trajectory despite the challenging upper-gastric anatomy and the difficulty of accessing the upper, gravity-dependent portion of the lesion located near the cardia, where scope stability was compromised. The overtube ensured consistent shaft control, reduced unintended movements, and allowed precise orientation toward both the upper and deeper parts of the lesion, enabling accurate dissection.

After submucosal injection, a circumferential incision was performed using a conventional ESD knife (DualKnife J, Olympus, Japan), followed by deep excavation-type dissection within the muscular layer using a hook-type ESD knife (HookKnife J, Olympus, Japan) under continuous clip-line traction. The GIST was cautiously separated from the muscularis propria without perforation, and removed en-bloc in a 150 min procedure. The post-ESD defect was completely closed using multiple clips.

The capsule of the resected specimen measureing 35 × 30 mm was intact . The combined use of a rigidizing overtube and traction methods provided excellent stability and precision, enabling safe and complete resection in an anatomically constrained region.

Histopathology confirmed a R0 resection of a 29 mm spindle-cell GIST with low mitotic activity (<5/5 mm²), positive staining for CD117 and DOG1, and no necrosis. The lesion was staged as pT2Nx.The postoperative course was uneventful, with no bleeding or perforation. Oral feeding resumed and the patient discharged in good condition the next day.Conservative surveillance using CT and endoscopy was proposed to the patient.

Described for the first time in the upper GI, this case illustrates that ESD assisted by a rigidizing overtube can facilitate safe and controlled resection of subepithelial gastric tumors arising from the muscularis propria, specifically in technically challenging locations such as the upper gastric body. The overtube improved scope stability and access, enabling precise dissection and complete en bloc R0 removal without the need for surgery.This stabilization-assisted approach may be particularly useful in selected cases of gastric GIST where anatomical constraints limit conventional ESD.