The most accurate way to detect lung cancer is to take biopsy or cytology for pathological examination of diseased lung tissues through bronchoscopy, transthoracic wall puncture or surgery, which is the gold standard for lung cancer diagnosis. However, in a few cases, if pathological or cytological evidence cannot be obtained, clinical diagnosis and treatment can also be made when combined with the patient’s clinical history and symptoms, such as cough, chest pain, hemoptysis, lung masses as well as pleural effusion visible on imaging, and increased tumor markers. Lung cancer is divided into non-small cell lung cancer and small cell lung cancer, and the tumor markers expressed by both are different according to the pathological types.