Version July 2025
| Primary tumor (T)* | |||
| T category | T criteria | ||
| TX | Primary tumor cannot be assessed | ||
| T0 | No evidence of primary tumor | ||
| T1 | Tumor limited to the thymus with or without encapsulation, or directly invades into the mediastinal fat only, or directly invades the mediastinal pleura but does not involve any other mediastinal structure | ||
| T1a | Tumor ≤5 cm in greatest dimension with either:
| ||
| T1b | Tumor >5 cm in greatest dimension with either:
| ||
| T2 | Tumor with direct invasion of the pericardium (either partial or full thickness), or the lung, or the phrenic nerve | ||
| T3 | Tumor with direct invasion into any of the following: brachiocephalic vein, superior vena cava, chest wall, or extrapericardial pulmonary arteries or veins | ||
| T4 | Tumor with direct invasion into any of the following: aorta (ascending, arch, or descending), arch vessels, intrapericardial pulmonary artery or veins, myocardium, trachea, esophagus | ||
Primary tumor suffix
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| Regional lymph nodes (N)* | |||
| N category | N criteria | ||
| NX | Regional lymph nodes cannot be assessed | ||
| N0 | No tumor involvement of regional lymph node(s) | ||
| N1 | Tumor involvement of anterior (perithymic) lymph nodes | ||
| N2 | Tumor involvement of deep intrathoracic or cervical lymph nodes (eg, paratracheal, subcarinal, aortopulmonary window, hilar, jugular, and/or supraclavicular nodes) | ||
Regional lymph nodes suffix
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| Distant metastasis (M)* | |||
| M category | M criteria | ||
| cM0 | No distant metastasis | ||
| cM1 | Distant metastasis | ||
| cM1a | Separate pleural or pericardial nodule(s) | ||
| cM1b | Pulmonary intraparenchymal nodule or other distant metastasis | ||
| pM1 | Microscopic confirmation of distant metastasis | ||
| pM1a | Microscopic confirmation of separate pleural or pericardial nodule(s) | ||
| pM1b | Microscopic confirmation of pulmonary intraparenchymal nodule or other distant metastasis | ||
| AJCC prognostic stage group is assigned based on the stage classification and categories chosen.* | |||
| Prognostic stage groups | |||
| When T is... | And N is... | And M is... | Then the stage group is... |
| T1a-T1b | N0 | M0 | I |
| T2 | N0 | M0 | II |
| T3 | N0 | M0 | IIIA |
| T4 | N0 | M0 | IIIB |
| Any T | N1 | M0 | IVA |
| Any T | N0-N1 | M1a | IVA |
| Any T | N2 | M0-M1a | IVB |
| Any T | Any N | M1b | IVB |
AJCC: American Joint Committee on Cancer; TNM: tumor, node, metastasis.
* AJCC data elements required for staging are identified with an asterisk.
