We hope that this introduction can help our patients and friends to get timely treatment through self-examination or early detection. The clinical manifestation of lung cancer is closely related to the location, size, type, development stage, and the presence of complications or metastasis of the tumor. There are 5%-15% of patients who are asymptomatic when lung cancer is detected. The main symptoms include the following aspects. I. Symptoms caused by primary tumor (a) Cough is a common early symptom, and tumor in the trachea may have irritating dry cough or small amount of mucus sputum. Alveolar cancer may have a large amount of mucus sputum. When tumor causes distal bronchial stenosis, the cough is aggravated, mostly persistent and with high-pitched metallic sound, which is a characteristic obstructive cough. When there is secondary infection, the sputum volume increases and is mucopurulent in nature. （Hemoptysis is often caused by the rich vascularity of cancerous tissues. Hemoptysis is most common in central type lung cancer, and is mostly blood in sputum or intermittent blood sputum. It is often not easy to attract patients’ attention and delay early diagnosis, but if it erodes large blood vessels, it may cause hemoptysis. (3) Wheezing Due to partial obstruction of bronchus caused by tumor, about 2% of patients can cause limited wheezing. (4) Chest tightness and shortness of breath Tumor causes bronchial stenosis, especially central type lung cancer; or tumor metastasizes to hilar lymph nodes and the enlarged lymph nodes compress the main bronchus or bulge; or metastasizes to pleura and a large amount of pleural effusion occurs; or metastasizes to pericardium and pericardial effusion occurs; or has diaphragm paralysis, superior vena cava obstruction and extensive lung involvement, all of which can affect lung function and cause chest tightness and shortness of breath. If the original chronic obstructive pulmonary disease, or combined with spontaneous pneumothorax, chest tightness and shortness of breath are more serious. (5) Weight loss Weight loss is one of the common symptoms of tumor. In advanced stage of tumor development, due to tumor toxin and consumption and infection, loss of appetite caused by pain, it can be manifested as wasting or cachexia. (6) Fever Generally, fever is caused by necrosis in tumor department. Most of the fever is caused by secondary pneumonia caused by tumor, and antibiotic drug treatment is not effective. Symptoms caused by local extension of tumor (a) Chest pain About 30% of tumors directly invade the pleura, ribs and chest wall, which can cause chest pain of different degrees. If the tumor is located near the pleura, it will produce irregular dull pain or hidden pain, and the pain will be aggravated when breathing or coughing. When the ribs and spine are invaded, there are pressure points, but not related to breathing and coughing. If the tumor compresses the intercostal nerve, the chest pain may involve its distribution area. (2) Dyspnea Tumor compression of large airway may cause inspiratory dyspnea. (3) Difficulty in swallowing Cancer invades or compresses the esophagus and causes difficulty in swallowing. (4) Hoarseness may occur when cancer directly compresses or metastasizes to the enlarged mediastinal lymph nodes and compresses the recurrent laryngeal nerve (mostly on the left side). (v) Superior vena cava compression syndrome When cancer invades the mediastinum and compresses the superior vena cava, the flow of the superior vena cava is blocked, resulting in edema of the head, face, neck and upper limbs, as well as bruising and varicose veins in the anterior thorax, which may cause headache and dizziness or vertigo. (6) Horner syndrome Lung cancer located in the apical part of the lung is called supraglottic carcinoma, which can compress the sympathetic nerve of the neck, causing ptosis of the eyelid on the side of the disease, pupil narrowing, inversion of the eyeball, and no or little sweating on the ipsilateral forehead and chest wall. Tumor compression on the brachial plexus often causes burning pain mainly in the axilla and radiating to the inner side of the upper limbs, especially at night.