Surgical treatment of gastric cancer is mainly divided into radical resection and palliative resection in clinical practice. Radical resection, also called curative resection, refers to the removal of the primary tumor together with regional lymph nodes and invaded tissues and organs, without tumor residue, thus making complete cure possible. Due to the different scope of lymph node removal, D1, D2, D3, etc. are often used to indicate the scope of radical surgery, according to which, radical surgery can be divided into absolute radical surgery and relative radical surgery. Absolute radical surgery refers to the extent of surgical clearance has sufficient safety range, such as patients with metastasis of the first station lymph nodes, DZ surgery to remove the second station lymph nodes is performed, the safety range of surgery is larger. If D1 surgery is performed to remove only the first station lymph nodes, the scope of surgery does not go beyond the station with metastatic lymph nodes, and the safety margin is smaller, so it is called relatively radical surgery. Even if the surgery is very thorough, it can only be called relatively radical surgery if the risk of lymph node removal is not completely removed due to other factors. For example, in the case of gastric cancer that has infiltrated into the extra-plasma membrane, the cancer cells may detach and cause the risk of peritoneal or pelvic implantation, so even if D3 or D4 surgery is performed to remove the lymph nodes at the third or even fourth station, the surgery cannot eliminate the risk of peritoneal or pelvic implantation. To express the extent of lymph node clearance, radical surgery is classified as D0, D1, D2, D3, and D4. D0: curative gastrectomy without total lymph node clearance at the first station (referred to as D0 or root 0 surgery). D1: curative gastrectomy with complete lymph node clearance at the first station (referred to as D1 or root 1 operation). D2: curative gastrectomy with total lymph node dissection at the second station (abbreviated as D2 or root 2). D3: curative gastrectomy with total lymph node dissection at the third station (referred to as D3 or root 3 surgery). D4: A curative gastrectomy in which the abdominal para-aortic lymph nodes are removed in addition to the radical D3 operation (abbreviated as D4 or root 4 operation). Palliative resection Also called non-curative resection. If the residual tumor is confirmed by pathology, it is called absolute non-curative resection; if the residual part is considered as tumor by visual observation but not confirmed by pathology, it is called relative non-curative resection.