It is possible for lung cancer to be asymptomatic, especially peripheral lung cancer, which usually does not cause symptoms such as coughing, coughing up sputum, chest tightness and breath-holding if it does not affect the large bronchial tubes. Even central type lung cancer can be asymptomatic if the tumor is particularly small. Some lung cancer patients even come to the clinic only when they have symptoms of distant metastasis, such as headache, dizziness, etc., and once they check the CT or MRI of the skull and brain, they find that there are metastases in the brain. For example, if a patient has headache or dizziness, a CT or MRI of the brain reveals metastases in the brain. It is only after further examination that a mass in the lung is found and bronchoscopy or aspiration biopsy is performed that the diagnosis of lung cancer is confirmed. Therefore, if there are no symptoms such as cough and sputum, it does not mean that there is no lung cancer in the body. Especially those who have long-term smoking need to have regular checkups every year to detect tumors and treat them as early as possible.