Early stage lung cancer can also show clinical symptoms of fever. Lung cancer is a malignant tumor of lung tissues, and clinical symptoms of fever may occur whether in early or late stage, because early stage lung cancer can also show infections. Since lung cancer is a malignant tumor, it will lead to the decrease of resistance and therefore easy to complicate infection, especially the infection of respiratory system, thus coughing and coughing up sputum, and also fever. During the process of necrosis, tumor tissues can also produce the symptom of fever, because tumor can stimulate the increase of cytokine level in the body, thus causing the clinical symptom of fever. Therefore, when early stage lung cancer patients have fever, it is necessary to clarify whether the fever is caused by the cancer itself or the fever is caused by the complication of infection.