How to check for lung cancer, firstly, for lung cancer screening, particularly in people over forty years old, especially smokers, it is recommended to regularly undergo low-dose spiral CT scans of the chest. Secondly, if a tumor is detected, it is suggested to proceed with enhanced CT scans, sputum cytology tests, or PET-CT. If it is confirmed that there is a tumor in the lungs, then a biopsy is needed. The biopsy can be performed under bronchoscopy, or transthoracic lung puncture and biopsy of living tissue can also be done, as well as biopsy of metastatic lesions or cytological examination of pleural effusion to diagnose whether it is lung cancer, the type of lung cancer, and certain immunohistochemical situations.