| Primary tumour (T) | |
| TX | Primary tumour cannot be assessed, or the tumour is proven by the presence of malignant cells in sputum or bronchial washing but is not visualised by imaging or bronchoscopy |
| T0 | No evidence of primary tumour |
| Tis | Carcinoma in situ |
| T1 | Tumour ≤3 cm in greatest dimension, surrounded by lung or visceral pleura, no bronchoscopic evidence of invasion, more proximal than the lobar bronchus (not in the main bronchus); superficial spreading of tumour in the central airways (confined to the wall of the trachea or mainstem bronchus) |
| T1a | Tumour ≤2 cm in the greatest dimension |
| T1b | Tumour >2 cm but ≤3 cm in the greatest dimension |
| T2 | Tumour >3 cm but ≤7 cm or tumour with any of the following: Invades visceral pleura Involves the main bronchus ≥2 cm distal to the carina Associated with atelectasis/obstructive pneumonitis extending to hilar region but not involving the entire lung |
| T2a | Tumour >3 cm but ≤5 cm in the greatest dimension |
| T2b | Tumour >5 cm but ≤7 cm in the greatest dimension |
| T3 | Tumour >7 cm or one that directly invades any of the following: Chest wall (including superior sulcus tumours), diaphragm, phrenic nerve, mediastinal pleura, or parietal pericardium Tumour in the main bronchus <2 cm distal to the carina but without involvement of the carina Associated atelectasis/obstructive pneumonitis of the entire lung or separate tumour nodule(s) in the same lobe |
| T4 | Tumour of any size that invades any of the following: mediastinum, heart, great vessels, trachea, recurrent laryngeal nerve, oesophagus, vertebral body, or carina Separate tumour nodule(s) in a different ipsilateral lobe |
| Regional lymph nodes (N) | |
| NX | Regional lymph nodes cannot be assessed |
| N0 | No regional node metastasis |
| N1 | Metastasis in ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes, including involvement by direct extension |
| N2 | Metastasis in the ipsilateral mediastinal and/or subcarinal lymph node(s) |
| N3 | Metastasis in the contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph nodes |
| Distant metastasis (M) | |
| MX | Distant metastasis cannot be assessed |
| M0 | No distant metastasis |
| M1 | Distant metastasis |
| M1a | Separate tumour nodule(s) in a contralateral lobe; tumour with pleural nodules or malignant pleural (or pericardial) effusion |
| M1b | Distant metastasis |
Reproduced from [18] with permission from the publisher.