The key to the diagnosis and treatment of lung cancer lies in “three early stages”, i.e. early detection, early diagnosis and early treatment. According to research, it is a slow process from the beginning of cancer in a certain part of lung tissue to the appearance of certain clinical symptoms and signs, which is a gradual process from quantitative to qualitative changes. This process is called “pre-cancer” in medical science. And this period is also the stage with the best treatment effect. Therefore, if we can pay attention to the early manifestations of lung cancer, it is conducive to early detection and early treatment. Therefore, if we can pay attention to the early manifestations of lung cancer, it will be beneficial to early detection and early treatment, so that we can prevent the disease from occurring in the future. Therefore, the following people should be alert: cough, hemoptysis and persistent chest pain are important signs of lung cancer, especially for those who are over 40 years old and have a long-term and heavy smoking history, they should think about the possibility of lung cancer. If you have a family history of lung cancer or other tumors or have been stimulated by adverse external factors, you should go to the hospital promptly if you feel unwell. 1. Cough is the earliest and most common symptom of lung cancer patients. Since it often resembles cold or bronchitis when it starts, it is easy to be ignored. Therefore, anyone who has no chronic respiratory disease in the past, especially those over 40 years old, should be alerted to the possibility of lung cancer and should undergo further examination if the cough persists for more than three weeks after active treatment. As for elderly patients with chronic bronchitis, the incidence of lung cancer is higher than that of the general population, but their early cough symptoms are often easily confused with their existing chronic cough, thus delaying the diagnosis in many cases. At this time, it is important to pay attention to the change of cough nature and cough pattern. Due to the stimulation of bronchial mucosa by cancer tissue, cough of lung cancer patients is often irritating choking cough and severe cough with little sputum, which is not in line with the original four seasons pathogenesis pattern, and the symptoms are aggravated by the ineffectiveness of active anti-infection treatment. 2. Hemoptysis is the second common symptom of lung cancer. It is often caused by the invasion of cancer tissue into bronchial mucosa. The amount of hemoptysis is usually very small, often in the form of blood sputum, and may last for several weeks or months, or may occur intermittently. Due to the small amount or intermittent occurrence of hemoptysis, it is easy to be neglected. In fact, about 1/4 of those who present with bloody sputum in middle age or older are due to lung cancer. Therefore, it is important not to be paralyzed when unexplained sputum and blood appear. 3. Chest pain accounts for more than half of lung cancer patients, especially peripheral lung cancer, chest pain can be the first symptom. That is due to the infiltration of cancer tissue into the pleura. Chest pain is often fixed at the lesion site, and in the early stage, it is mostly intermittent hidden pain and discomfort. It can be aggravated by postural changes, deep breathing and coughing. Therefore, any unexplained chest pain with fixed location should be examined early.