Solid lung nodules with clear borders are generally more likely to be benign than those with unclear nodule borders and are less serious, but require long-term follow-up observation. Lung nodules are focal, rounded, hyperdense, solid or sub-solid lung shadows with a diameter of ≤3 cm on imaging. Lung nodules can be categorized into solid and sub-solid lung nodules according to their density. Solid lung nodules are characterized by round or round-like hyperdense shadows in the lungs, and the density of the lesion is sufficient to obscure the traveling blood vessels and bronchial shadows. For the differentiation of benign and malignant, in general, the probability of malignancy increases as the size of the lung nodule increases, but it is also necessary to closely combine the changes in morphology and density. Morphologically, malignant lung nodules are often lobulated or have burr signs (or spiny protrusions), while most benign lung nodules are not lobulated, and the edges may have sharp corners or fibrous bands, etc. The presence of fibrous bands and pleural thickening around them often suggests that the nodules are benign. In addition, the margins of malignant lung nodules are usually clear but not smooth, and the nodule-lung interface is rough or even has burrs, while the margins of benign non-inflammatory lung nodules are usually clear and smooth. Regular follow-up is recommended to monitor the condition of the nodules and prompt treatment is recommended if there is a tendency for malignancy.