Lung cancer stage IIIA is the staging of the lung cancer condition, and the condition in this stage may be in one of T1N2M0, T2N2M0, T3N1M0, T3N2M0 in TNM staging. The TNM staging system is the most common international tumor staging system. Currently, the 2016 international TNM staging for lung cancer is used.TNM staging is based on three conditions: T (tumor primary focus), N (regional lymphatic and involvement), and M (whether metastasis is from the distal end) to stage the cancer. Clinical staging of lung cancer is divided into stages I, II, III and IV based on TNM staging. Lung cancer stage IIIA includes the following four conditions: 1. T1N2M0, i.e. the maximum diameter of the tumor is ≤3cm, no peripheral metastasis, ipsilateral mediastinal or subglottic lymph node metastasis, and no distant metastasis. 2、T2N2M0，i.e., 3cm＜tumor maximal diameter≤5cm or spreading to the hilum with lung atelectasis, ipsilateral mediastinal or subglottic lymph node metastasis, no distant metastasis. 3, T3N1M0, i.e. 5cm＜maximum diameter of the tumor≤7cm, or invasion of pericardium, chest wall, phrenic nerve, or isolated cancerous nodule in the same lobe, peribronchial or ipsilateral hilar lymph node metastasis, no distant metastasis. 4. T3N2M0, i.e. 5cm＜maximum diameter of tumor≤7cm, peribronchial or ipsilateral hilar lymph node metastasis, no distant metastasis. Lung cancer stage IIIA is one of the above four cases, the specific situation needs to be staged under the guidance of doctors.