MKI67 and breast cancer: A significant relationship was also found between Ki67 and tumor grade, as tumors with higher grades have higher levels of cell proliferation and are consequently more invasive than the other grades; these findings were consistent with the findings of other studies.27,28 In the present study, tumors with higher Ki67 expression showed a higher HER2/neu overexpression as well; this correlation may be used to predict the biological behavior of breast cancer.