This Randomized, Single-center Trial Aims to Evaluate the Advantages of Underwater ESD (U-ESD) in Comparison to the Conventional ESD (C-ESD).

Underwater ESD (U-ESD): after filling the lumen with saline and sucking all the air, initial submucosal injection of saline and methylene blue is performed; subsequent mucosal incision with ESD knife all around the lesion and submucosal dissection deep in the submucosal layer leading to an en bloc resection is carried out

Conventional ESD (C-ESD): under CO2 insufflation, initial submucosal injection of saline and methylene blue is performed; subsequent mucosal incision with ESD knife all around the lesion and submucosal dissection deep in the submucosal layer leading to an en bloc resection is carried out.