The severity of a lung nodule is related to the nature of the nodule, which is usually not serious if the patient’s nodule is benign and more serious if the patient’s intrapulmonary nodule is malignant. Therefore, when a patient’s chest X-ray or lung CT shows an intrapulmonary nodule, the nature of the nodule is evaluated. If the patient has a small diameter nodule with smooth margins, it is considered a benign nodule. If the nodule is larger in diameter with unsmooth margins and burr sign, it is considered to be a malignant nodule with a high probability. It can be further identified by sputum cancer cell examination, bronchoscopy and puncture biopsy. If cancer cells are detected in the patient’s sputum or detected by bronchoscopic puncture biopsy, the nodule can be diagnosed as malignant nodules, and the condition is serious and needs active treatment.