Table I. TNM staging of non-small cell lung cancer.

T
T0		No evidence of primary tumor.
Tis		Carcinoma in situ.
T1		Tumor that is ≤3 cm in its greatest dimension, does not invade the visceral pleura, and is without bronchoscopic evidence of invasion more proximal than a lobar bronchus. The uncommon superficial spreading tumor of any size with its invasive component limited to the bronchial wall, which may extend proximal to the main bronchus, is classified as a T1a.
	T1a	Tumor is ≤2 cm in its greatest dimension.
	T1b	Tumor is >2 cm, but ≤3 cm, in its greatest dimension.
T2		Tumor with any of the following characteristics: >3 cm but ≤7 cm in its greatest dimension, invades a mainstem bronchus with its proximal extent at least 2 cm from the carina, invades the visceral pleura, or is associated with either atelectasis or obstructive pneumonitis that extends to the hilar region without involving the entire lung.
	T2a	Tumor is >3 cm, but ≤5 cm, in its greatest dimension.
	T2b	Tumor is >5 cm, but ≤7 cm, in its greatest dimension.
T3		Tumor with any of the following characteristics: >7 cm in its greatest dimension; invades the chest wall (including superior sulcus tumors), diaphragm, phrenic nerve, mediastinal pleura, parietal pericardium, or a mainstem bronchus less than 2 cm from the carina without invasion of the carina; is associated with either atelectasis or obstructive pneumonitis of the entire lung; or separate tumor nodule(s) are located in the same lung lobe as the primary tumor.
T4		Tumor of any size that invades the mediastinum, heart, great vessels, trachea, recurrent laryngeal nerve, esophagus, vertebral body, or carina; or separate tumor nodule(s) located in a different lobe of the ipsilateral lung.
N
N0		No regional lymph node involvement.
N1		Involvement of ipsilateral intrapulmonary, peribronchial, or hilar lymph nodes.
N2		Involvement of ipsilateral mediastinal or subcarinal lymph nodes.
N3		Involvement of contralateral mediastinal or hilar lymph nodes. Alternatively, involvement of either ipsilateral or contralateral scalene or supraclavicular lymph nodes.
M
M0		No distant metastasis.
M1		Metastasis.
	M1a	Malignant pleural effusion, pericardial effusion, pleural nodules, or metastatic nodules in the contralateral lung.
	M1b	Distant (extrathoracic) metastasis.