A 4mm nodule in the lung is a relatively small nodule in the lung, only 4mm. If the patient has no obvious symptoms, he or she can be clinically observed for 3-6 months and then have the chest CT rechecked; if it does not grow, then continue clinical observation; if it grows, then go to the hospital for CT-guided puncture or surgical thoracoscopy to remove it. Generally speaking, pulmonary nodules are often seen in inflammation, tuberculosis, lung tumors and other diseases, if it is a benign disease, the prognosis is often better, if it is a malignant disease, you need to do timely surgery, depending on the situation to decide whether to carry out radiotherapy, chemotherapy and other treatment, usually to strengthen nutrition, exercise, increase body resistance.