Endoscopic findings. ( A) Conventional endoscopy before multiple biopsies at a medical checkup in November 2009 showed a submucosal tumor-like polypoid lesion with a central deep depression. ( B) In work-up prior to surgery in May 2010, conventional endoscopy showed a submucosal tumor-like polypoid lesion with a depression. The lesion was decreased in height and had tense surface mucosa compared with the lesion seen during the initial esophagogastroduodenoscopy at the medical checkup in November 2009. ( C) Chromoendoscopy after spraying indigo carmine solution revealed a marginal portion of the polypoid lesion covered by normal duodenal mucosa. The depressed portion showed an irregular margin. ( D) Narrow-band imaging magnified endoscopy revealed an obscure mucosal pattern with irregular microvessels in the depressed portion (arrows).