Lung cancer is currently the number one cause of cancer deaths worldwide. The distribution of lung cancer is more in the right lung than in the left lung, more in the upper lobe than in the lower lobe, and cancer can occur from the main bronchi to the fine bronchi. Lung cancer originating from the main bronchus and lobar bronchus and located close to the lung door is called central lung cancer; lung cancer originating below the bronchus of the lung segment and located in the peripheral part of the lung is called peripheral lung cancer. High-risk factors of lung cancer Those who have a history of smoking and smoking index greater than 400 cigarettes/year, a history of high-risk occupational exposure (e.g. exposure to asbestos) and a family history of lung cancer, and those who are over 45 years old are the high-risk group of lung cancer. 1. Early stage of lung cancer may have no obvious symptoms. When the disease develops to a certain extent, the following symptoms often appear: (1) Irritating dry cough. (2) Blood in sputum or bloody sputum. (3) Chest pain. (4) Fever. (5) Shortness of breath. When the respiratory symptoms cannot be relieved after treatment for more than two weeks, especially blood in sputum, irritating dry cough, or aggravation of the existing respiratory symptoms, the possibility of lung cancer should be highly alerted. 2.When lung cancer invades surrounding tissues or metastases, the following symptoms may appear: (1) Hoarseness when the cancer invades the recurrent laryngeal nerve. (2) The cancer invades the superior vena cava, and the symptoms of superior vena cava obstruction syndrome such as facial and neck edema may appear. (3) The cancer invades the pleura and causes pleural effusion, which is often bloody; a large amount of effusion can cause shortness of breath. (4) The cancer invades the pleura and chest wall, which can cause continuous severe chest pain. (5) Upper lobe apical lung cancer can invade and compress the organ tissues located at the entrance of the thorax, such as the first rib, subclavian artery and vein, brachial plexus nerve and cervical sympathetic nerve, producing severe chest pain, upper limb venous anger, edema, arm pain and upper limb movement disorder, ipsilateral upper eye and face drooping, pupil narrowing, eye sunken, facial sweating and other cervical sympathetic syndrome manifestations. (6) Recent neurological symptoms and signs such as headache, nausea, vertigo or blurred vision should be considered as possible brain metastases. (7) Bone metastasis should be considered for persistent bone pain at fixed sites and elevated plasma alkaline phosphatase or blood calcium. (8) Right upper abdominal pain, hepatomegaly, elevated alkaline phosphatase, glutamic transaminase, lactate dehydrogenase or bilirubin should be considered as possible liver metastases. (9) Nodules may be palpated under the skin in case of subcutaneous metastasis.