Lung cancer is one of the fastest growing malignant tumors in terms of incidence and mortality, and one of the most threatening to the health and lives of the population. The cause is still not fully clear, but a lot of information shows that long-term heavy smoking has a very close relationship with the occurrence of lung cancer. Studies have proven that long-term heavy smokers are 10 to 20 times more likely to develop lung cancer than non-smokers, and the younger the age of starting to smoke, the higher the chance of developing lung cancer. Early lung cancer mainly manifests as the following symptoms 1. cough is the most common symptom, and cough as the first symptom accounts for 35% to 75% of people. The cough caused by lung cancer may be related to changes in bronchial mucus secretion, obstructive pneumonia, pleural invasion, pulmonary atelectasis and other intrathoracic comorbidities. When the tumor grows in the bronchial mucosa above the segment with larger diameter and sensitive to foreign stimulation, it can produce cough caused by foreign body-like stimulation, typically manifesting as paroxysmal irritating dry cough, which is often not easily controlled by general cough suppressants. When the tumor grows in the smaller bronchial mucosa below the segment, the cough is not obvious, or even no cough. For patients who smoke or suffer from chronic bronchitis, if the degree of coughing worsens, the number of frequency changes, and the nature of coughing changes such as high pitched metallic sound, especially in the elderly, they should be highly alert to the possibility of lung cancer. Blood in sputum or hemoptysis is also a common symptom of lung cancer, and about 30% of patients have this as their first symptom. Due to the rich blood supply and brittle texture of tumor tissues, the blood vessels may rupture and cause bleeding when coughing vigorously. Coughing up blood in lung cancer is characterized by intermittent or persistent, repeatedly small amount of blood in sputum or small amount of hemoptysis. 3. Chest pain is the first symptom of about 25% of patients. It often appears as irregular hidden pain or dull pain in the chest. In most cases, peripheral type lung cancer invades the wall pleura or chest wall, which can cause sharp and intermittent pleuritic pain, and if it continues to develop, it will evolve into constant drilling pain. Mild chest discomfort that is difficult to localize is sometimes associated with central lung cancer invading the mediastinum or involving blood vessels or peribronchial nerves, while 25% of patients with malignant pleural effusion complain of dull chest pain. Persistent sharp and severe chest pain that is not easily controlled by drugs often indicates extensive pleural or chest wall invasion. Persistent pain in the shoulder or back of the chest suggests the possibility of tumor invasion in the inner lobe of the lung near the mediastinum. About 10% of patients have chest tightness and shortness of breath as the first symptom, which are mostly seen in central type lung cancer, especially in patients with poor lung function. The causes of dyspnea mainly include: (1) When lung cancer is advanced and the mediastinal lymph nodes are widely metastasized and compress the trachea, rhomboid or main bronchus, shortness of breath or even asphyxia may appear. (2) When a large amount of pleural effusion compresses lung tissue and causes serious displacement of mediastinum, or when there is pericardial effusion, chest tightness, shortness of breath and dyspnea may also appear, but the symptoms can be relieved after fluid extraction. (3) Diffuse fine bronchoalveolar carcinoma and bronchial disseminated adenocarcinoma, which reduce the respiratory area and impair gas diffusion, leading to severe ventilation/blood flow ratio imbalance, causing progressive worsening of dyspnea, often accompanied by cyanosis. (4) Other: including obstructive pneumonia. Pulmonary atelectasis, lymphadenopathy, tumor microembolism, upper airway obstruction, spontaneous pneumothorax, and combined chronic lung diseases such as COPD. 5. Hoarseness is the first complaint in 5% to 18% of lung cancer patients, usually accompanied by cough. Hoarseness generally indicates direct mediastinal invasion or lymph node growth involving the ipsilateral recurrent laryngeal nerve, resulting in left vocal fold paralysis. Vocal cord paralysis may also cause upper airway obstruction of varying degrees.