Lung cancer is not a contagious disease and people with lung cancer do not infect people. Lung cancer is a disease in which external causes act through internal causes, and the external causes that may cause cancer include smoking, ionizing radiation, fungal toxins, air pollution, occupational dust and chemical fumes. Exogenous factors act on the lungs to cause irreversible genetic changes and induce malignant transformation of cells, but have nothing to do with contagion. The development of lung cancer is related to the condition of the patient’s organism. Patients with recurrent chronic infections, such as bronchiectasis, chronic obstructive pulmonary disease, tuberculosis, etc., whose bronchial epithelium undergoes chronic infections may transform into squamous epithelium and thus lead to cancer, but it is not related to infection. Lung cancer is also associated with genetic factors, such as genetic susceptibility and familial aggregation of lung cancer, which plays an important role in people and individuals who are susceptible to environmental carcinogens. Relatives with a family history of early lung cancer are twice as likely to have lung cancer, but it is not associated with transmission. Lung cancer is usually characterized by coughing up sputum, coughing, bloody sputum or hemoptysis with symptoms such as shortness of breath, chest pain, hoarseness, low-grade fever, and lethargy, etc. Surgical resection, radiotherapy, chemotherapy, and immunotherapy can be used in the treatment of lung cancer.