Stroke and lung cancer may seem to be two diseases that are not related to each other. In fact, the first symptom of lung cancer patients is stroke, which accounts for about 16% according to medical data. How can stroke be so close to lung cancer? There are two main reasons for lung cancer patients to have stroke: 1. Lung cancer patients mostly have increased coagulation factors, increased blood viscosity and thrombosis, which leads to cerebral thrombosis and stroke. On the other hand, lung cancer is prone to brain metastasis, and cancer cells may involve the brain, cerebellum and brainstem, damaging the brain function, and patients show symptoms similar to stroke, such as unclear language expression, limited limb movement and even hemiparesis. Patients usually first consult neurology. Since stroke is a common and frequent disease in the elderly, not only patients but also neurologists do not consider the lung cancer factor when stroke-like symptoms appear. There are also many patients who have no pulmonary symptoms, which further conceals the condition. Sometimes patients are treated as if they had an ischemic stroke, but often the results are not good and the condition tends to get progressively worse before the lung tumor is detected by chest radiography. Therefore, when stroke occurs in the elderly, it is important to consider the possibility of lung cancer and have a routine chest X-ray to exclude lung cancer so as not to delay treatment. It should be especially reminded that lung cancer generally does not have any symptoms in early stage because the tumor does not touch the trachea, so there will be no coughing symptoms; the tumor does not touch the pleura, so there will be no chest pain; the tumor does not invade and destroy the bronchial mucosa and surrounding blood vessels, so there will be no hemoptysis. Therefore, in order to detect lung cancer at an early stage, regular physical examination and chest X-ray should be taken. Especially for those who have a history of smoking and are over 40 years old, chest X-ray should be taken once every six months to once a year. If you have a cough that does not improve after half a month of treatment, you should have your chest X-ray taken in time. If you have a cough with blood in the sputum and chest pain that is fixed in a certain place, you should also have a lung X-ray and CT examination.