Local and systemic symptoms caused by tumor (1) Cough: the most common symptom of lung cancer, mostly irritating dry cough, no sputum or little white mucus sputum. (2) Bloody sputum: it is the most typical symptom of lung cancer, mostly bloody sputum or sputum with blood. Blood sputum is caused by the invasion of microscopic blood vessels of bronchial mucosa by cancer tumor, often mixed with shed cancer cells, and the positive rate of sputum cytology examination is high. (3) Chest tightness and chest pain: In the early stage, it only shows mild chest tightness, but when the cancer tumor involves the wall pleura or directly invades the chest wall, it can cause constant and continuous pain in the area. (4) Shortness of breath: obstructive pneumonia or atelectasis caused by tumor blocking bronchi is one of the causes of shortness of breath in lung cancer, and malignant pleural fluid caused by pleural dissemination of lung cancer is also a cause of shortness of breath. In addition, diffuse alveolar carcinoma leading to interstitial lung lesions can cause shortness of breath due to hyperventilation, and in severe cases, it can cause difficult to treat dyspnea. (5) Fever: Obstructive pneumonia is the main cause of fever in lung cancer. This kind of fever is characterized by recurrence, sometimes good and sometimes bad, and difficult to be cured. In addition, fever can also be caused by cancer toxin or bone marrow metastasis. (6) Non-specific systemic symptoms: loss of appetite, weight loss, cachexia in advanced stage, etc. The symptomatology of lung cancer is not specific and is similar to the clinical manifestations of many respiratory diseases. Therefore, the key to rely on symptomatology to diagnose lung cancer is to be alert to lung cancer. Any respiratory symptoms that are untreated for more than two weeks should be highly alert to the possibility of the existence of lung cancer. Symptoms of lung cancer invasion and metastasis (1) Superior vena cava obstruction syndrome: caused by direct invasion of lung cancer or metastasis of right upper mediastinal lymph nodes compressing the superior vena cava, which is manifested as edema of head and neck or even both upper limbs, anger of neck and upper chest veins and capillary dilation. This is the first symptom in 5-10% of lung cancer patients. (2) Horner’s syndrome; caused by lung cancer or metastatic lymph nodes involving the sympathetic nerve from the 7th cervical vertebra to the lateral side of the 1st thoracic vertebra. (3) Pancoast syndrome: Based on Horner syndrome, the tumor further destroys the 1st and 2nd ribs and the brachial plexus nerve, causing pain in the upper limbs. Other common symptoms of invasion and metastasis include: hoarseness due to involvement of laryngeal nerve; headache, vomiting and hemiparesis due to brain metastasis; persistent pain at the corresponding site due to bone metastasis. Accompanying symptoms of lung cancer (1) pulmonary hypertrophic osteoarthropathy: It is mostly seen in patients with lung adenocarcinoma, with an incidence of about 12%, followed by squamous lung cancer. The main clinical manifestations are pain in the large joints of bones, pestle-like fingers and toes, and the diagnosis can be based on periosteal hyperplasia or periostitis of long bones on X-ray. (2) Carcinoid syndrome: The main clinical manifestations are abdominal pain and diarrhea, facial flushing, and bronchospasm. The carcinoid syndrome is caused by bioactive amines produced by silver-loving cells in cancerous tissues. It is worth mentioning that carcinoid syndrome is mostly seen in small cell lung cancer, while carcinoid syndrome does not occur in bronchial carcinoid tumors. (3) Gynecomastia: The main clinical manifestation is bilateral or unilateral breast development. It may be caused by the production of ectopic gonadotropins by lung cancer, mostly seen in small cell lung cancer. Other concomitant symptoms of lung cancer include hypercalcemia caused by ectopic parathyroid-like material; cancerous neuropathy and myopathy, dermatomyositis; eosinophilia; Cushing’s syndrome and antidiuretic hormone excess.