The differences between pulmonary nodular disease and lung cancer include: different nature of the disease, different causes of the disease, different treatment principles and different prognosis. 1. Different nature of diseases: pulmonary nodular disease is an interstitial lung disease, which is benign; while lung cancer is a malignant tumor of lung. 2. Different causes: the cause of pulmonary nodular disease is still unclear, which may be related to heredity, certain pathogen infections, immune factors, etc., while lung cancer is unknown, and its risk factors include smoking, environmental air pollution, occupational factors, and ionizing radiation. 3. Different treatment principles: Lung nodular disease is mainly treated by internal medicine, asymptomatic or stable early stage patients usually do not need to be treated, and can be treated with glucocorticoids, methotrexate, azathioprine and other medicines when symptoms appear; whereas lung cancer is mainly treated by comprehensive treatment, including surgery, chemotherapy, radiotherapy, targeted therapy, immunotherapy and so on. 4. Different prognosis: the condition of patients with pulmonary nodular disease can remain stable for a long time, and most of them have good prognosis. A small number of patients can develop serious pulmonary fibrosis or multiple organ damage, thus affecting the survival time, and the overall mortality rate is about 1%~5%; while lung cancer is a malignant tumor with high degree of malignancy, and most of the patients will die within a few years if they are not treated in time, and the overall 5-year survival rate is less than 20%.