Unexpected endoscopic full-thickness resection of a duodenal neuroendocrine tumor

Figure 1 A neuroendocrine tumor, 5 mm in diameter, was detected in the duodenal bulb during endoscopy in an asymptomatic 57-year-old man.

Figure 2 Although a blue-colored layer was identified in the resection defect, a small amount of a whitish layer was detected above the blue layer.

Figure 3 The defect was immediately closed with endoclips.

Figure 4 The muscle layer was clearly located on the underside of the resected specimen.

Figure 5 The muscularis propria was detected just beneath the submucosal layer (hematoxylin-eosin staining, loupe image).