Gastric inverted polyp successfully resected by underwater endoscopic mucosal resection.

A 47-year-old man, who underwent an annual esophagogastroduodenoscopy as part of his routine check-up, was found to have a small subepithelial lesion on the posterior wall of the gastric body in 2013. The lesion gradually increased in size during follow-up. In 2024, 11 years after the initial detection, the lesion had grown to over 10 mm in diameter and exhibited central erythematous depression. Endoscopic ultrasonography was performed, revealing that the lesion originated from the second layer with uniformly low internal echogenicity. A biopsy suggested the possibility of a benign stromal tumor, but a definitive diagnosis was not achieved. To obtain a complete biopsy, en bloc resection was performed using underwater endoscopic mucosal resection. Histopathological examination confirmed the diagnosis of a gastric inverted polyp. Since gastric inverted polyps with central depression or erosion have the potential for malignancy, endoscopic resection is recommended.