Lung cancer is a malignant tumor that cannot be examined by tumor markers. The main examination means for lung cancer is to do lung CT scan and enhancement to detect lung occupying lesions. Then, fiberoptic bronchoscopy or pathological puncture biopsy will be performed for the occupying lung lesions. Puncture biopsy can clearly identify lung cancer if cancer cells can be found, and tumor markers have no place in the diagnosis of lung cancer. Although lung adenocarcinoma can manifest as elevated carcinoembryonic antigen levels, even elevated carcinoembryonic antigen levels cannot confirm the diagnosis of lung cancer. Lung cancer can only be diagnosed by fiberoptic bronchoscopy or puncture biopsy, and nothing else is a diagnostic method for lung cancer.