Gastric cancer staging is routinely performed using the TNM staging system. This article is based on the 8th edition of the AJCC TNM classification of malignant tumors. This is technically the clinical TNM staging (cTNM).
cTNM staging (8th edition)
T
Tx: primary tumor cannot be assessed
T0: no evidence of primary tumor
Tis: carcinoma in situ: intraepithelial tumor without invasion of the lamina propria, high grade dysplasia
-
T1
T1a: tumor invades the lamina propria and or muscularis mucosae
T1b: tumor invades submucosa
T2: tumor invades muscularis propria
T3: tumor penetrates the subserosal connective tissue without invasion of the visceral peritoneum or adjacent structures
-
T4
T4a: tumor invades the serosa (visceral peritoneum)
T4b: tumor invades adjacent structures
N
Nx: regional lymph node (s) cannot be assessed
N0: no regional nodal involvement
N1: metastases in 1 to 2 regional lymph nodes
N2: metastases in 3 to 6 regional lymph nodes
-
N3
N3a: metastases in 7 to 15 regional lymph nodes
N3b: metastases in more than 15 regional lymph nodes
M
M0: no distant metastases
M1: distant metastases
In this edition, pN3 is divided into pN3a and pN3b, and pT1N3b and pT2N3b are considered stage IIIB. Furthermore, pT3N3b is classified as stage IIIC, pT4bN0 and pT4aN2 are downstaged from stage IIIB into stage IIIA, and pT4aN3a and pT4bN2 from stage IIIC into stage IIIB 3.