4mm microscopic nodules include mixed ground-glass nodules, pure ground-glass nodules, and solid nodules, which need to be reviewed and followed up.
1. Solid nodules: Most of the 4mm solid nodules are of low malignancy, but if one of the risk factors is age ≥40 years, smoking ≥20 packs/year, history of high-risk environmental or occupational exposure such as asbestos exposure, history of combined diffuse pulmonary fibrosis or tuberculosis, history of previous malignancy or family history of lung cancer, then it is a high-risk patient, and requires 12-month review of chest CT.
2. Mixed ground-glass nodules: 4mm mixed ground-glass nodules need to be reviewed by chest CT at 3, 6, 12 and 24 months, and those with no change can be converted to routine annual examination.
3. Pure ground-glass nodule: 4mm pure ground-glass nodule can be followed up at 6 months and then annually.
It is recommended that patients consult a specialist to make a comprehensive judgment based on the density and shape of the nodule, and follow the doctor’s instructions for follow-up or treatment.