Endoscopic Mucosal Resection Versus Endoscopic Submucosal Dissection for Colorectal Laterally Spreading Lesions.

Inclusion Criteria: * Adults (at least 18 years old). * LSL-NG FE type ≥ 20mm or LST-G mixed type ≥30mm who have not been previously treated or received submucosal injection, regardless of their location in the colon. * LSL-NG FE type ≥ 20mm or LST-G mixed type ≥30mm WITHOUT a demarcated area * The patient must have undergone a complete colonoscopy, reaching the cecum, to detect possible synchronous lesion. If this procedure has not been done previously, it will be performed prior to the inclusion of the patient in the study. * Patients able to fill in questionnaires written in Spanish or English. Exclusion Criteria: * Contra-indication to colonoscopy. * Contra-indication to general anesthesia. * Inability to stop antiplatelet agents and anti-coagulant according to the European Society of Gastro-Intestinal Endoscopy guidelines. * Patients with \> 1 lesion meeting the inclusion criteria. * LSL-NG FE type ≥ 20mm or LST-G ≥30mm mixed type that have been previously treated (Recurrence or residual lesion after previous endoscopic or surgical treatment). * LSL-NG FE type ≥ 20mm or LST-G ≥30mm mixed type with previous submucosal injection, even if a resection attempt with a snare was not finally performed. * Lesions with suspicion of deep submucosal invasive carcinoma: depression or invasive pit-pattern (Vi within a demarcated area or Vn). * Submucosal mass like elevation within a LSL-NG FE type. * LSLs having a previous biopsy or tattooing. Previous biopsies of the lesion should only be allowed if LSL-G mixed type \> 30 mm and samples were taken out of the flat area. * LSL-G with a Buddha like deformation (Polyp on polyp) * LSL involving a surgical anastomosis. * LSL involving the appendicular orifice. * LSL involving the terminal ileum. * Patient's refusal to participate in the study * Presence of inflammatory bowel disease * Pregnant or lactating women. * Hereditary colorectal cancer syndrome or hereditary polyposis. * Patient under legal protection and or deprived of liberty by judicial or administrative decision. * Patient already participating in an interventional clinical research protocol * Patient who cannot be followed for the duration of the study. * Inability to sign the informed consent of the study.