Molten glass nodules with well-defined borders have a higher likelihood of being benign and therefore better, while those with poorly defined borders have a higher risk of malignancy. Lung nodules are categorized into solid nodules, pure ground-glass nodules, and mixed ground-glass nodules based on the density of the nodules on imaging such as chest CT, and the latter two together are called ground-glass nodules. Milled glass nodules may be caused by benign diseases such as pneumonia, misshapen tumors, sarcoidosis, rheumatoid nodules, etc., or malignant tumors such as lung metastatic carcinoma, bronchopulmonary carcinoma, etc. The risk of malignancy is higher in mixed milled glass nodules than in solid nodules. Generally, the boundaries of lung nodules caused by benign neoplastic diseases such as malignant tumors are clear; inflammatory diseases such as pneumonia can lead to blurring of the boundaries of lung nodules due to inflammatory exudation; and malignant tumors such as bronchopulmonary carcinoma can lead to unclear boundaries of the nodules due to their invasive nature. Therefore, the risk of malignancy is lower in well-defined nodules than in those with blurred borders. However, the diagnosis of malignancy cannot be made solely on the basis of the smoothness of the nodule edges, and the risk of malignancy should be assessed in conjunction with the size and shape of the nodule, as well as the patient’s age, history of lung disease, and family history, etc. Pathologic examination is the gold standard for confirmation of the diagnosis. Patients are advised to consult a specialist for further evaluation and treatment.