MKI67 and breast cancer: Proliferative activity, in general, has been shown to be a significant factor in determining the prognosis of breast cancer [1,40,41,42], and the monoclonal Ki-67 antibody has been consistently shown to be an independent prognostic biomarker in breast cancer patients [43], with multiple studies showing a correlation between the Ki-67 proliferation index and breast cancer survival [2,43,44,45,46,47,48,49].