The reasons of blood in sputum in late stage of lung cancer may be primary symptoms caused by tumor, secondary infection and other reasons.
1. Primary symptoms caused by tumor: mostly seen in central lung cancer, the tumor grows into the lumen and may invade the bronchial arteries and other blood vessels in the lungs, resulting in rupture of blood vessel wall and bleeding, which will be coughed out with sputum when coughing. In addition, the abnormal enlargement of tumor tissue may cause ischemia, necrosis and rupture, which may also cause bleeding.
2. Blood in sputum due to secondary infection: Lung cancer is often complicated by infection of lung bronchus, which causes the increase of secretion and the symptoms of cough and blood in sputum.
Blood in sputum of lung cancer is mostly suggestive of rupture of blood vessels in lungs, and it is recommended to standardize treatment under the guidance of professional doctors.