Lung cancer immunohistochemistry ki67 is 40% represents a positive rate of 40%, high malignant degree of lung cancer, fast tumor growth, high metastatic rate of lung cancer, higher recurrence rate after cure, poorer prognosis and high sensitivity to radiotherapy. When ki67 is generally greater than 15%, it is suggestive of high malignancy of lung cancer and high metastatic recurrence rate. When the positive rate is 40%, it is necessary to pay more attention to the prognosis, closely observe the lymphatic and blood changes, and review regularly. ki67 is cell proliferation-related nuclear antigen, closely related to the malignant degree of the tumor, which is usually 0 in normal cells, but ki67 can not be the only basis for judging the benign or malignant nature of the tumor, and further examination is needed.