5mm Lung nodules with clear margins are most often the result of benign lung disease and tend to be less serious, but there is a lower risk that they are the result of lung cancer, which is more serious. Lung nodules are one of the imaging manifestations of most benign and malignant lung diseases. Generally 5mm nodules have a low risk of malignancy, about 1%, and clear margins are also mostly a benign sign. 5mm nodules are more likely to be caused by benign lung diseases, such as pneumonia, tuberculosis, sarcoidosis, malignant tumors, etc., which can be improved or cured by timely treatment, and are usually not serious. 5mm lung nodules also have a lower risk of being malignant nodules, i.e. caused by malignant tumors such as bronchopulmonary carcinoma, which are more serious and require timely radical surgery, chemotherapy and other treatments. However, 5mm lesions are mostly early stage lung cancers with better prognosis after timely treatment. It is recommended that patients should consult the doctor in time and follow the medical advice for follow-up, further examination or treatment.