Underwater endoscopic mucosal resection of upper gastrointestinal subepithelial tumors: A case series pilot study (with video).

Introduction: Underwater endoscopic mucosal resection (UW-EMR) has been recently introduced as an effective technique for rectal third layer subepithelial tumors. Therefore, we aimed to assess the safety, efficacy, and procedure time of UW-EMR for upper gastrointestinal subepithelial tumors (SETs) originating from the deep mucosal and/or submucosal layers.

Methods: Between August 2018 to July 2022, a total of 17 SETs (7 duodenal SETs, 6 gastric SETs, and 4 esophageal SETs) were included in this study. On endoscopic ultrasound examinations, the tumors were found to be embedded in the submucosa without muscularis propria invasion. All SETs were resected successfully using UW-EMR. The characteristics of the tumors and their R0 resection rate, adverse event rate, and recurrence rate were evaluated retrospectively.

Results: The mean tumor size was 0.9 cm (range, 0.3-1.5 cm). En bloc resection and complete resection rates were 100%, respectively. The patients showed no complications such as perforation or bleeding. Histologic assessments of the resected tumors revealed 9 neuroendocrine tumors (7 on the duodenum, 2 on the stomach), 2 gastric cystica profunda, 1 gastric follicular lymphoma, 1 gastric fibromyxoma, 3 esophageal granular cell tumors, and 1 esophageal adenoid cystic carcinoma. The mean procedural time was 3.2 min (range, 1.3-8.7 minutes). The overall en bloc and complete resection rates were 100%, respectively. No recurrence was observed during the follow-up period.

Conclusion: UW-EMR is a safe and effective treatment for upper gastrointestinal SETs embedded in the submucosal layer. Further studies are needed to compare other endoscopic resection techniques.