Microscopic nodules in lungs may not necessarily turn into lung cancer. If the nodules are found to increase in size during the review, they may be cancerous, but there is no exact time point for how long they can turn into cancer in clinical practice. If the lung nodules have clear boundary and no burr sign, they are mostly benign nodules and do not need special treatment. If the lung nodules are found to be enlarged, with unclear borders and adhesions with surrounding tissues, they may have undergone malignant transformation and need bronchoscopy and aspiration cytology for clear diagnosis. Early diagnosis and early treatment of lung cancer will lead to better prognosis. In addition, lung cancer malignancy is related to many factors. Regular work and rest, avoiding overwork, quitting smoking and alcohol can reduce the possibility of lung nodule malignancy.