Pathologic findings are the gold standard for whether a lung ground glass nodule is carcinoma in situ. Lung ground glass nodule means that the lesion is cloudy and thin shadow like ground glass in the imaging. Lung ground glass nodules are divided into pure ground glass nodules and mixed ground glass nodules, which are mostly the imaging manifestations of lung adenocarcinoma. Pure ground-glass nodule refers to the lesion manifesting as ground-glass-like, without solid component. The pathology of pure ground glass nodules has the possibility of lung carcinoma in situ. Mixed ground-glass nodule refers to ground-glass nodule mixed with solid components, the more solid components, the higher degree of malignancy, and the pathology is mostly micro-invasive adenocarcinoma, invasive adenocarcinoma and so on. Pneumonic ground-glass nodules require percutaneous lung aspiration biopsy or surgical resection to define the pathological type and stage. Most of the ground-glass nodules are inert and progress slowly, and can be followed up by dynamic review of chest CT to observe the changes of the lesions. Note: If the image shows ground glass nodule, there is no need to be overly anxious, nor can we leave it alone, we need to review low-dose CT in regular hospitals, and follow up regularly, during the observation period, the lesion becomes larger or the solid component increases, we need to consult regular hospitals, and if necessary, percutaneous lung puncture biopsy or surgical resection is necessary to clarify the pathology.