En bloc resection of intestinal-type adenoma extending to the minor duodenal papilla by underwater endoscopic mucosal resection with a forward-viewing endoscope.

We report successful en bloc underwater endoscopic mucosal resection (UEMR) of a lesion involving the minor duodenal papilla. A woman in her 60s presented with a 10-mm depressed lesion in the descending duodenum. White-light imaging and Magnifying endoscopy suggested a tumor involving a minor papilla. Although side-viewing endoscopes are conventionally used for the minor papilla, pre-procedural assessment indicated inadequate maneuverability for this specific lesion (ED-580T; Fujifilm Corporation, Tokyo, Japan). Consequently, we strategically used a forward-viewing dual-channel endoscope (GIF-2TQ260M; Olympus Medical Systems, Tokyo, Japan). Utilizing its right-side instrument channel and independent suction capability provided a direct approach and stable field of view, facilitating precise snaring. Histopathology confirmed a 15 × 13-mm intestinal-type adenoma with negative margins. Given the minor papilla was located at the tumor margin and lacked a luminal orifice, the lesion was diagnosed as a superficial non-ampullary duodenal epithelial tumor (SNADET) secondarily extending to the papilla. Forward-viewing endoscopes are viable alternatives for this region depending on lesion orientation. Furthermore, comprehensive pre-procedural assessment, including evaluation for pancreas divisum, may aid in determining treatment strategies, such as the omission of pancreatic stenting. Strategic, case-specific endoscope selection is paramount for safe therapeutic intervention in this complex anatomical region.