The TNM system, which is recommended by WHO, is used to classify cancer in the esophagus. The system is based on the extensiveness of the local tumor (T), degree of lymph node spreading (N), and metastases (M).
Tumor Infiltration (T)
- T1: Infiltration in the lamina propria or submucosa
- T2: Infiltration in the mucularis propria
- T3: Infiltration through the adventitia, but not into other organs/structures
- T4: Infiltration into adjacent structures
Lymph Node Status (N)
- N0: No regional lymph node metastases
- N1: Regional lymph node metastases
- M0: No metastases
- M1: Metastases
For cervical esophageal cancer, mediastinal lymph node metastases are classified as M1.
For upper thoracic esophageal cancer, metastasis to cervical and supraclavicular lymph nodes is classified as M1a. Metastasis to coeliac lymph nodes is classified as M1b.
For mid thoracic esophageal cancer, metastasis to supraclavicular lymph nodes is classified as M1b and coeliac as M1b.
For lower thoracic esophagus cancer, metastasis to supraclavicular lymph nodes is classified as M1b and coeliac as M1a.