Generally, the higher the Ki67 of malignant tumors, the more likely to metastasize, and different tumors and experimental centers use different Ki67 values as the cut-off values for high and low expression. Ki67 is a tumor proliferation-associated antigen, which is a reliable indicator of tumor proliferative activity due to the absence of G0 phase with nuclear quiescence and short half-life. Generally, the higher the Ki67 positive rate, the more active the tumor proliferation, the more likely to recurrence and metastasis, and the worse the prognosis. Different tumors have different Ki67 positivity rates as negative and positive thresholds, as well as high and low expression thresholds. For example, breast cancer generally takes 20%~30% as the high and low expression threshold; cervical cancer and gastric cancer generally takes 10% as the negative and positive threshold, and 25% as the high and low expression threshold; thymoma takes 50% as the high and low expression threshold. Different experimental methods and different pathology centers may have different thresholds, and the local pathology center report should be referred to determine the Ki67 positivity rate. In addition, whether the tumor is prone to metastasis is also related to the presence of lymph node metastasis, tumor size, histological grading and other factors, and it is recommended that the patient combine with other clinical data to make a comprehensive judgment.