Table 1. TNM (tumour, node, metastasis) classification for lung cancer
Primary tumour (T)
    TXPrimary 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
    T0No evidence of primary tumour
    TisCarcinoma in situ
    T1Tumour ≤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)
    T1aTumour ≤2 cm in the greatest dimension
    T1bTumour >2 cm but ≤3 cm in the greatest dimension
    T2Tumour >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
    T2aTumour >3 cm but ≤5 cm in the greatest dimension
    T2bTumour >5 cm but ≤7 cm in the greatest dimension
    T3Tumour >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
    T4Tumour 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)
    NXRegional lymph nodes cannot be assessed
    N0No regional node metastasis
    N1Metastasis in ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes, including involvement by direct extension
    N2Metastasis in the ipsilateral mediastinal and/or subcarinal lymph node(s)
    N3Metastasis in the contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph nodes
Distant metastasis (M)
    MXDistant metastasis cannot be assessed
    M0No distant metastasis
    M1Distant metastasis
    M1aSeparate tumour nodule(s) in a contralateral lobe; tumour with pleural nodules or malignant pleural (or pericardial) effusion
    M1bDistant metastasis
  • Reproduced from [18] with permission from the publisher.