T, N and M Descriptors of the 7th Edition for Lung Cancer Staging
T– Primary Tumor
Tx - Primary tumor cannot be assessed, or tumor proven by the presence of malignant cells in sputum or bronchial washings but not visualized by imaging or bronchoscopy T0 - No evidence of primary tumor Tis - Carcinoma in situ T1 - Tumor 3 cm or less in greatest dimension, surrounded by lung or visceral pleura, without bronchoscopic evidence of invasion more proximal than the lobar bronchus (i.e., not in the main bronchus)  T1a - Tumor 2 cm or less in greatest dimension1  T1b - Tumor more than 2 cm but not more than 3 cm in greatest dimension T2 - Tumour more than 3 cm but not more than 7 cm; or tumour with any of the following features2:
  • Involves main bronchus, 2 cm or more distal to the carina
  • Invades visceral pleura
  • Associated with atelectasis or obstructive pneumonitis that extends to the hilar region but does not involve the entire lung
 T2a - Tumor more than 3 cm but not more than 5 cm in greatest dimension  T2b - Tumor more than 5 cm but not more than 7 cm in greatest dimension T3 - Tumor more than 7 cm or one that directly invades any of the following: Chest wall (including superior sulcus tumors), diaphragm, phrenic nerve, mediastinal pleura, parietal, pericardium; or tumour in the main bronchus less than 2 cm distal to the carina1 but without involvement of the carina; or associated atelectasis or obstructive pneumonitis of the entire lung or separate tumour nodule(s) in the same lobe as the primary T4 - Tumor of any size that invades any of the following: mediastinum, heart, great vessels, trachea, recurrent laryngeal nerve, esophagus, vertebral body, carina; separate tumour nodule(s) in a different ipsilateral lobe to that of the primary
N – Regional Lymph Nodes
Nx - Regional lymph nodes cannot be assessed N0 - No regional lymph node metastasis N1 - Metastasis in ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes, including involvement by direct extension N2 - Metastasis in ipsilateral mediastinal and/or subcarinal lymph node(s) N3 - Metastasis in contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph node(s)
M – Distant Metastasis
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 effusion3  M1b - Distant metastasis
Notes: 1The uncommon superficial spreading tumour of any size with its invasive component limited to the bronchial wall, which may extend proximal to the main bronchus, is also classified as T1a 2T2 tumors with these features are classified T2a if 5 cm or less or if size cannot be determined, and T2b if greater than 5 cm but not larger than 7 cm 3Most pleural (pericardial) effusions with lung cancer are due to tumor. In a few patients, however, multiple microscopical examinations of pleural (pericardial) fluid are negative for tumor, and the fluid are non-bloody and is not an exudate. Where these elements and clinical judgment dictate that the effusion is not related to the tumour, the effusion should be excluded as a staging element and the patient should be classified as M0
Table 1: Complete T, N and M descriptors in 7th edition for lung cancer staging [3,21].