Division of Research and Development for Minimally Invasive Treatment;
Cancer Center;
School of Medicine;
Keio University;
Tokyo 160-8582;
Japan;
Division of Endoscopy;
National Cancer Center Hospital;
Tokyo 160-8582;
Japan;
Endoscopic; submucosal; dissection; Colonoscopy; Colorectum; Complication; Perforation; Training;