A Study to Explore Prognoses of the Patients With N2 Non-small Cell Lung Cancer

Inclusion Criteria:

* Patients with radical resection of lung cancer enrolled from 2014 to 2019;
* Pathologically diagnosed patients with non-small cell lung cancer;
* Patients with age \> 18 years old;
* Patients who did not receive chest surgeries before hospitalization;
* Patients with N2 lymph nodes (+) after surgeries;
* Patients who received lymphadenectomy for one group or more groups of lymph nodes;

Exclusion Criteria:

* Patients with second primary tumors or multiple primary tumors;