About 1/4 of patients have lung cancer detected during physical examination or group X-ray/CT examination for other reasons, but have no symptoms. The symptoms of lung cancer are affected by the primary and metastatic lung cancer foci, and also related to the abnormal hormones secreted by the tumor. The most common early symptoms of primary lung cancer include cough, bloody sputum/blood in sputum, chest pain, shortness of breath, etc. 1. Cough: About 50% of lung cancer patients have cough symptoms. The newly appeared cough symptoms should be paid enough attention, especially for smokers and former smokers. Cough symptoms are mostly caused by the stimulation of bronchial mucosa by tumor and often have poor effect on conventional drug treatment. Irritating cough that persists for a long time or even worsens after treatment requires consultation with a professional physician to exclude the possibility of lung cancer. 2. Bloody sputum/blood in sputum: It is a more specific symptom of lung cancer and exists in about 20% of patients. Inflammation, necrosis or rupture of capillaries secondary to tumor often cause a small amount of bleeding, which is mixed with sputum and then coughed out. This symptom may occur continuously or intermittently. Intermittent symptoms are easily overlooked, thus delaying treatment. Therefore, any bloody sputum/sputum with blood needs to be ruled out as a diagnosis of lung cancer until the cause is clear. Some central lung cancers may lead to massive hemoptysis, which is a lung cancer emergency and requires urgent interventional treatment or even emergency surgery. 3. Chest pain: About 25% of lung cancer patients have chest pain symptoms. Early stage lung cancer patients have mild chest pain and often lack clear pain localization. If the pain is persistent, severe and the location of pain is clear, it may indicate that the tumor has involved the pleura or even the chest wall. In a few patients, the chest pain is caused by bone metastases and bone scan is feasible for differentiation. 4.Shortness of breath: about 30% of lung cancer patients have shortness of breath symptoms. It is often caused by the obstruction of bronchus by tumor. Very few patients have extra-pulmonary symptoms as the first symptom. When the tumor has not yet metastasized or even in the early stage of lung cancer, the tumor has already affected the distant organs and caused dysfunction, which we call “paraneoplastic syndrome”. The common extra-pulmonary manifestations of early lung cancer include pestle and mortar, anemia, muscle weakness, skin rash, encephalopathy, weight loss, fatigue, hyponatremia and so on. Some patients can further search through the paraneoplastic syndrome to detect the primary lung lesion in a more timely manner.