The main factors that determine the prognosis of gastric cancer include the degree of tumor differentiation, the depth of tumor invasion into the stomach wall, lymph node metastasis, and the presence of liver and lung metastasis and intra-abdominal implant metastasis. Considering the above factors, the prognosis of the tumor can be generally predicted. What is the degree of tumor differentiation? The differentiation degree of tumor is generally divided into 4 grades, i.e. grade I, II, III and IV. Grade I has the best differentiation, tumor cells are closer to normal cells and generally has a good prognosis; grade IV has the worst differentiation, high malignancy and generally has a poor prognosis. Which layers can the stomach wall be divided into? The stomach wall can be divided into mucosal layer, submucosal layer, muscle layer and plasma layer. The tumor can be divided into T1, T2, T3 and T4 stages according to the depth of tumor invasion; T1 stage tumor is confined to the submucosal layer and has the best surgical effect; T4 stage tumor invades the surrounding organs and usually requires combined organ resection. There are about 20 groups of perigastric lymph nodes, which are generally divided into 3 stations, the first station is closest to gastric cancer and the third station is farthest from gastric cancer. If gastric cancer has distant metastasis such as liver and lung, or abdominal implantation, it is advanced stage and often cannot be removed surgically.