Table 1. TNM classification of lung cancer in the 6th edition (5, 6) and proposal for the 7th edition (25).

	6th edition		Proposal for the 7th edition
T	TX	Primary tumor cannot be assessed, or evidence of malignant cells in sputum or bronchial lavage fluid but no visualization of tumor on imaging or bronchoscopy	TX	Primary tumor cannot be assessed, or evidence of malignant cells in sputum or bronchial lavage fluid but no visualization of tumor on imaging or bronchoscopy
	T0	No evidence of primary tumor	T0	No evidence of primary tumor
	Tis	Carcinoma in situ	Tis	Carcinoma in situ
	T1	Tumor ≤ 3 cm greatest diameter, surrounded by lung tissue or visceral pleura, no bronchoscopic evidence of invasion proximal to the lobar bronchus (i.e., main bronchi are free)*1	T1	Tumor ≤ 3 cm greatest diameter, surrounded by lung tissue or visceral pleura, no bronchoscopic evidence of infiltration proximal to the lobar bronchus (i.e., main bronchi are free)*1
			T1a	Tumor ≤ 2 cm greatest diameter
			T1b	Tumor > 2 but ≤ 3 cm greatest diameter
	T2	Tumor > 3 cm or tumor with one of the following features:	T2	Tumor > 3 but ≤ 7 cm with one of the following features:
		invasion of the main bronchus, ≥ 2 cm dis tal to the carina invasion of the visceral pleura associated atelectasis or obstructive pneumonia extending as far as the hilus but not involving the whole lung		invasion of the main bronchus ≥ 2 cm distal to the carina invasion of the visceral pleura
				Associated atelectasis or obstructive pneumonia extending as far as the hilus but not involving the whole lung
			T2a	Tumor > 3 but ≤ 5 cm greatest diameter
			T2b	Tumor > 5 but ≤ 7 cm greatest diameter
	T3	Tumor of any size with direct invasion of one of the following structures:	T3	Tumor > 7 cm or any tumor with direct invasion of one of the following structures:
		chest wall (including tumors of the superior sulcus) diaphragm phrenic nerve mediastinal pleura parietal pericardium		chest wall (including tumors of the superior sulcus) diaphragm phrenic nerve mediastinal pleura parietal pericardium
		or tumor in the main bronchus < 2 cm distal to the carina, without involvement of the carina and without associated atelectasis or obstructive pneumonia of the whole lung		or tumor in the main bronchus < 2 cm distal to the carina, without involvement of the carina and without associated atelectasis or obstructive pneumonia of the whole lung or satellite tumor nodule(s) in the same lobe
	T4	Tumor of any size invading one of the following structures:	T4	Tumor of any size invading one of the following structures:
		mediastinum heart great vessels trachea recurrent laryngeal nerve esophagus vertebral body carina		mediastinum heart great vessels trachea recurrent laryngeal nerve esophagus vertebral body carina or separate tumor nodule(s) in another ipsilateral lobe
		or separate tumor nodule(s) in the same lobe or tumor with malignant pleural* 2 or pericardial effusion
N	NX	Regional lymph nodes could not be evaluated	NX	Regional lymph nodes could not be evaluated
	N0	No regional lymph node metastases	N0	No regional lymph node metastases
	N1	Metastasis/metastases in the ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary lymph nodes, including involvement by direct extension of the primary tumor	N1	Metastasis/metastases in the ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary lymph nodes, including involvement by direct extension of the primary tumor
	N2	Metastasis/metastases in the ipsilateral mediastinal and/or subcarinal lymph nodes	N2	Metastasis/metastases in the ipsilateral mediastinal and/or subcarinal lymph nodes
	N3	Metastasis/metastases in the contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene or supraclavicular lymph nodes	N3	Metastasis/metastases in the contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene or supraclavicular lymph nodes
M	MX	Distant metastases could not be evaluated	MX	Distant metastases could not be evaluated
	M0	No distant metastases	M0	No distant metastases
	M1	Distant metastases, including separate tumor nodules in another pulmonary lobe	M1	Distant metastases
			M1a	Separate tumor nodule(s) in a contralateral lobe; tumor with pleural*2 nodes or malignant pleural (or pericardial) effusion
			M1b	Distant metastases

^*1 A superficially extending tumor with invasion limited to the bronchial wall is always classified as T1.

^*2 In patients with lung cancer, pleural and pericardial effusions are usually due to the tumor. In a few patients, however, if multiple cytological examinations are negative for the presence of tumor cells, the effusion is not hemorrhagic and is not an exudate. If these factors are present, and if the clinical evaluation also indicates that the effusion is not caused by the lung cancer, the effusion should not be taken into account as a staging criterion.