S2.

TNM staging of esophageal carcinoma (AJCC 8th edition 2017)

Definitions of primary tumor, regional lymph node, distant metastasis for esophageal carcinoma
Primary tumor (T)
TX Tumor cannot be assessed
T0 No evidence of primary tumor
Tis High-grade dysplasia
T1 Tumor invades the lamina propria, muscularis mucosae 　　 or submucosa
T1a Tumor invades the lamina propria or 　　 muscularis mucosae
T1b Tumor invades the submucosa
T2 Tumor invades the muscularis propria
T3 Tumor invades adventitia
T4 Tumor invades adjacent structures
T4a Tumor invades the pleura, pericardium, azygos 　　 vein, diaphragm or peritoneum
T4b Tumor invades other adjacent structures, such as 　　 the aorta, vertebral body or airway
Regional lymph node (N)
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Metastasis in one to two regional lymph nodes
N2 Metastasis in three to six regional lymph nodes
N3 Metastasis in seven or more regional lymph nodes
Distant metastasis (M)
M0 = No distant metastasis
M1 = Distant metastasis