Whether a pulmonary ground glass nodule is malignant or not depends on the size and nature of the nodule. The main analysis is as follows: 1. Do not consider malignancy: ground glass nodules less than 5mm or even less than 3mm are mostly seen as benign nodules. It is recommended to follow up once a year with a high resolution CT of the chest. If the ground glass nodule is between 6-8mm, it is recommended to follow up once in three months, and if the nodule has no change, it is still not considered malignant. 2. Alert to malignant change: If the nodule is accompanied by short burr, lobar sign, pleural depression sign, pleural traction sign, and shows growing nodal change, it needs to be highly alert to the possibility of malignant change. Therefore, the chance of malignant change of the ground glass nodule depends mainly on whether the ground glass nodule is a growing nodule, whether the size is larger than 8mm, and whether it is accompanied by pleural depression, pleural traction, short burr, and lobar sign.