A “6×4 mm solid lung nodule” is usually a medium-risk nodule for lung cancer, and its severity is determined by the changes and nature of the nodule, and its risk of malignancy is relatively low. They need to be followed up routinely. Lung nodules can be categorized into partially solid nodules, ground glass density nodules and solid nodules, among which solid nodules have the lowest risk of malignant transformation. The risk assessment criteria and follow-up strategies for solid lung nodules are as follows: 1. Risk assessment criteria: solid nodules with a length and diameter between 5 mm and 15 mm and without obvious malignant CT signs are intermediate-risk nodules for lung cancer. 2. Follow-up strategy: Follow-up should be carried out after 3 months to observe the growth characteristics, and the growth of the nodules found should be included in the treatment of high-risk nodules, while the non-growth should continue to be followed up for 2 years. If physical examination reveals solid nodules in the lungs, attention should be paid to them, and they should go to regular hospitals in time to improve relevant examinations and draw up the next diagnosis and treatment plan.