Sixteen non-ampullary duodenal neoplasms in 16 patients were treated with endoscopic submucosal dissection (ESD) performed by an endoscopist and an instrument assistant between February 2011 and November 2014. En bloc resection was performed in 15 cases (94%); lateral and vertical margins were pathologically free in 13 cases. Perforation occurred during submucosal dissection using a flex knife,...