A pulmonary nodule is a physician’s description of the imaging presentation of a lesion seen on lung imaging. It refers to focal, round-like dense shadows of various sizes, with clear or blurred margins, and ≤3 cm in diameter on lung imaging. Symptoms vary depending on the cause. Common causes include lung cancer, tuberculosis, and pulmonary malformation tumor. 1. Lung cancer: there may be no obvious symptoms, and symptoms appear only after the disease has developed to a certain stage. For example, cough, blood in sputum, wheezing, chest pain, etc. Extrapulmonary manifestations, such as headache and pestle finger, may appear due to tumor invasion to adjacent organs and distant metastasis. 2. Tuberculosis: Inactive tuberculosis may not have any clinical manifestations and is only found during imaging examination. Active tuberculosis may present with cough, sputum, blood in sputum or hemoptysis as the disease progresses. It is often accompanied by low-grade fever, night sweats and other systemic symptoms. 3. Lung malformation tumor: there are no obvious symptoms in the early stage, and it is often found during physical examination. When the tumor develops to a certain size, it will cause bronchial stenosis or obstruction due to irritation or compression of bronchial tubes, resulting in cough, sputum, chest pain and other symptoms. In severe cases, symptoms such as dyspnea and cyanosis may occur. There are many other causes of lung nodules, such as pneumonia, etc. If lung nodules are found during the examination, the examination should be improved in time to clarify the cause of the disease and standardize the treatment under the guidance of doctors.