Early symptoms of lung cancer are often mild and may even be uncomfortable. Central lung cancer symptoms appear earlier and are more severe. Peripheral lung cancer symptoms appear later and are milder, or even without obvious symptoms, and are often detected during physical examination. The symptoms of lung cancer are roughly divided into local symptoms, systemic symptoms, extra-pulmonary symptoms, infiltration and metastasis symptoms, and the local symptoms mainly include: 1. Cough. Cough is the most common symptom of lung cancer. Cough caused by lung cancer may be related to changes in bronchial mucus secretion, obstructive pneumonia, pleural invasion, pulmonary atelectasis and other intrathoracic comorbidities. 2. Blood in sputum or coughing blood. Blood in sputum or coughing up blood is a common symptom of lung cancer. Due to the rich blood supply and brittle texture of tumor tissues, blood vessels rupture and cause bleeding when coughing vigorously. Coughing up blood may be caused by local necrosis of tumor or vasculitis.3. Chest pain is often manifested as irregular hidden pain or dull pain in the chest area. In most cases, peripheral type lung cancer invades the wall pleura or chest wall, which can cause sharp and continuous pleural pain, and evolve into constant stabbing pain if it continues to develop.4. Chest tightness and shortness of breath. When lung cancer has extensive mediastinal lymph node metastasis in advanced stage and presses the tracheal ridge or main bronchus, shortness of breath or even suffocation symptoms will appear. Large amount of pleural effusion compresses lung tissue and causes serious displacement of mediastinum, which can lead to chest tightness and shortness of breath.