T stage (depth of infiltration) T1: tumor invaded the intrinsic mucosal layer, myxomucosal layer (M) or submucosal layer (SM); T1a(M): tumor invaded the intrinsic mucosal layer, myxomucosal layer (M); T1b(SM): tumor invaded the submucosal layer (SM). T2(MP): tumor invaded the intrinsic muscular layer(MP). T3(SS): tumor invaded the subplasma layer(SS). T4: tumor invaded the plasma membrane (SE), or adjacent tissue (SI); T4a(SE): tumor invaded the plasma membrane (SE); T4b(SI): tumor invaded the adjacent tissue (SI). Note: Tumor penetrating the muscular layer, entering the gastrocolic or hepatogastric ligament, or entering the greater or lesser omentum, but not penetrating the visceral peritoneum covering these structures, is defined as T3, and if penetrating the visceral peritoneum tumor is defined as T4. N stage (number of lymph node metastases) N1: 1~2; N2: 3-6; N3: ≥7; N3a: 7-15; N3b: ≥16. M staging Liver metastasis (H1); peritoneal metastasis (P1); positive abdominal exfoliative cell examination (CY1); other distant organ metastasis (Ml); metastasis other than gastric regional lymph nodes. Note: Gastric regional lymph nodes: including No.1~No.12 and No.14v (in case of esophageal infiltration, No.19, No.20, No.110, No.111 are also regional lymph nodes), except for the lymph node metastasis defined as M1. NO8a, NO12a are regional lymph nodes, NO8p, NO12b, NO12p are defined as M1.