Figure 1.

A, A large, flat-elevated tumor located in the duodenal bulb (retroflexed view). B, Endoscopic submucosal dissection strategy before traction. 1: Mucosal incision on the proximal side of the tumor (yellow arrows). 2: Submucosal dissection of the posterior wall side of the tumor and creation of a mucosal flap (highlighted in blue). 3: Circumferential mucosal incision is completed (red arrows). C, Three clip-and-threads were deployed to the distal edges of the specimen (each numbered threads with syringes). D, Excellent visualization of the submucosal layer is achieved.