The gold standard of lung cancer diagnosis is pathological diagnosis, and the diagnosis of lung cancer is generally divided into four levels of diagnosis, as follows: 1) clinical diagnosis, doctors judge whether lung cancer has occurred according to patients’ clinical symptoms, but such diagnosis is uncertain; 2) imaging diagnosis, mainly through chest X-ray, CT, MRI and even PET-CT, which are common in clinical practice. At present, PET-CT is the most important imaging examination to diagnose lung cancer, but its accuracy rate is only 95%; 3. Pathological diagnosis: pathological diagnosis is made on the tissue obtained from lung puncture biopsy, and pathological diagnosis is the gold standard for lung cancer diagnosis, which means that any expert can question the clinical and other diagnoses and imaging diagnosis obtained, or even give different opinions. However, if the pathological diagnosis of lung puncture biopsy is obtained, the gold standard of tumor diagnosis can be reached. After reaching the gold standard, no one can question on the basis of imaging diagnosis or clinical diagnosis; 4. Genetic diagnosis: If the pathological diagnosis is obtained, the tissue of lung puncture biopsy is used for genetic sequencing, through which the genetic sequencing can discover the characteristics of the genetic level of tumor existence, that is, to observe whether there are genetic mutations or whether there are meaningful driver genes.