Currently, the staging of lung cancer is determined according to the 8th edition of TNM staging of lung cancer. If the primary tumor is 3-4 cm combined with or simply with pleural metastasis, the T stage is T2a; if the tumor is 4-5 cm and involves the pleura, the T stage is T2b; if the tumor is 5-7 cm or even larger and involves the pleura, the stage reaches T3 or T4; however, clinical staging is based on a combination of T stage of the primary tumor, N stage of regional lymph nodes and M stage of distant metastasis. For example, if the patient involves the pleura and the tumor is between 3-4 cm, the T stage is considered T2a. Combined with whether the regional lymph node metastasis and distant metastasis, the clinical stage can evolve from early stage IIa to stage IIb or III, or even stage IV.