TNM classification for gastric cancer

Tx: Primary tumor cannot be assessed

T0: No evidence of primary tumor

Tis: High-grade dysplasia/carcinoma in situ

T1a: Tumor invades lamina propria or muscularis mucosae

T1b: Tumor invades submucosa

T2: Tumor invades muscularis propria

T3: Tumor invades subserosal connective tissue without invasion of visceral peritoneum or adjacent structures (spleen, transverse colon, liver, diaphragm, pancreas, abdominal wall, adrenal gland, kidney, small intestine, or retroperitoneum); intramural extension to duodenum or esophagus is not considered as invasion to an adjacent structure, but is classified by the depth of greatest invasion in any of these sites; tumor may penetrate muscularis propria with extension into gastrocolic or gastrohepatic ligaments, or into the greater or lesser omentum, without perforation of visceral peritoneum covering these structures

T4a: Tumor invades visceral peritoneum

T4b: Tumor invades adjacent structures/organs (spleen, transverse colon, liver, diaphragm, pancreas, abdominal wall, adrenal gland, kidney, small intestine, or retroperitoneum)