What are the main symptoms of lung cancer? Early lung cancer clinical symptoms are not obvious. Lung cancer growing in the bronchial tubes mostly manifests as irritating cough, coughing sputum, blood in sputum, or different symptoms due to tumor invasion to different tissues and organs around. Peripheral lung cancer usually has no symptoms in early stage, or only limited transient chest pain. The main modes of metastasis of lung cancer include local spread (diffusion of the primary tumor to the surrounding tissues) lymphatic metastasis and hematogenous metastasis. The local spread of central lung cancer mostly invades the organs in the mediastinum and causes corresponding symptoms: if it compresses or invades the esophagus, it may cause symptoms similar to those of esophageal cancer, which manifests as gradually increasing difficulty in swallowing. Some patients complain of anterior chest and back pain, which is caused by the tumor infiltrating the mediastinal tissue and fixing the mediastinum and pulling it. If the tumor invades the pericardium, it may cause pericardial effusion with shortness of breath, tachycardia and other symptoms. When peripheral lung cancer invades local pleura, ribs or intercostal nerve, it may cause pain in the corresponding area; when the pleura is widely invaded, it may form malignant pleural fluid. Tumors near the spine may directly invade the vertebral body and cause local pain or other corresponding symptoms. Lymphatic metastasis is the main way of lung cancer metastasis. Intrathoracic metastasis can reach the hilar lymph nodes and/or mediastinal lymph nodes. The most common extrathoracic lymph nodes are supraclavicular or cervical lymph nodes, and some patients often present with an incidental finding of a supraclavicular or cervical mass. These masses are hard and immobile, but rarely painful. In the presence of mediastinal lymph node metastasis, the presence of abdominal lymph node metastasis should be noted. Hematogenous metastasis is another important metastatic route. Since lung cancer is a systemic disease, hematogenous metastasis can occur at an early stage. The sites of lung cancer metastasis are bones, brain, liver, adrenal gland and kidney in order: bone metastasis is asymptomatic in early stage, but pain may appear in late stage. The pain is characterized by fixed location, gradually worsening, and heavier at night than during the day; brain metastasis in early stage has no symptoms, or may only show mild depression or excitement, but can be detected by brain CT or MRI. Adrenal metastases are usually asymptomatic and are usually detected by abdominal CT or B-ultrasound. Lymph node metastasis is common in mediastinal lymph node metastasis, which is asymptomatic in the early stage and can be manifested as abdominal mass or intestinal obstruction in the late stage. In short, any of the above metastases can be the first sign of lung cancer and should be alerted.