The causes of lung malignant tumors, some researches have found that the factors closely related to lung malignant tumors or lung cancer are as follows:1. Smoking: some researches have found that the incidence rate of lung cancer in patients who have smoked for a long period of time, especially those who have smoked more than 1 pack of cigarettes every day, is more than 25 times of normal people, so it can be imagined that smoking is just like a chimney smoked to lungs and it will lead to the occurrence of cancerous changes of lungs cells. 2. Occupational and environmental factors: Some people who work in industrial environment for a long time, such as long-term exposure to asbestos, vinyl chloride and formalin, can lead to higher incidence of lung cancer. 3. Ionizing radiation. There is a kind of radioactive gas called radon gas, which is more common in mines, and the incidence of lung cancer of miners who inhale these gases is obviously higher.4. Previous lung infections: such as tuberculosis, chronic bronchial dilatation, the repeated stimulation of these chronic inflammation, the squamous epithelium of lungs can lead to the occurrence of cancer.5. Hereditary factors: if there is a lung cancer incidence in the family in the past, such a person has to be careful, and the incidence of lung cancer is higher than normal people. incidence of lung cancer is significantly higher than normal people.