Endoscopic submucosal dissection for the diagnosis and therapy of pedunculated gastric cancer with prolapse into the duodenal bulb: A case report.

•Preoperative diagnosis of gastric cancer invasion is not always sufficiently accurate.•We encountered a patient with the gastric cancer of which the pre-operative diagnosis of the invasion was indeterminable.•Diagnostic ESD was performed.•Pathohistological diagnosis revealed that the resection was curative and met the expanded criteria for ESD, so gastrectomy was not required.