Most of the pre-symptoms of lung cancer are not typical, however, if the following symptoms occur, you should be highly alert: 1.Inciting cough, especially cough with metallic sound, blood in the sputum or fresh blood in the whole mouth, which is not treated for a long time, and if inflammation and tuberculosis are excluded, you should highly suspect lung cancer. 2.Unexplained chest pain, that is, vague stabbing pain. 3.Low fever, especially in the afternoon. 4.Unexplained weight loss in the near future. Do not let down your guard just because you are young or there is no family history of lung cancer in your family before.