Breast cancer lung metastasis may not show any manifestation initially, but as the lung metastases increase in size, the following manifestations gradually appear: 1. Cough: It is the most common symptom of lung metastases, usually paroxysmal, irritating dry cough, without sputum or coughing little white mucus sputum. 2. Bloody sputum: It can be manifested as blood in sputum, and hemoptysis may appear when the bleeding volume is relatively large. The appearance of bloody sputum is caused by the tumor invading the microscopic blood vessels of bronchial mucosa. 3. Chest tightness or chest pain: In the early stage, it only shows mild chest tightness, but when the tumor involves the wall pleura or directly invades the chest wall, it can cause constant and continuous pain in this area. 4. Fever: The growth of tumor in bronchus is more likely to cause obstructive pneumonia, which is the main cause of fever. 5. Shortness of breath: When When the tumor blocks the bronchus, it will cause obstructive pneumonia or pulmonary atelectasis, resulting in shortness of breath. In addition, malignant pleural fluid caused by pleural dissemination is also the cause of shortness of breath. 6. Non-specific systemic manifestations: such as loss of appetite, weight loss, cachexia, etc.