MKI67 and breast cancer: Many of our findings agree with the literature that breast cancer in older women generally displays less aggressive features for example, low expression of Ki67 (a marker of proliferation), ALDH (a breast cancer stem cell), EGFR (a growth factor receptor related to HER2) and p53 (a gene which promotes tumorigenesis) and high expression of BCL2 (an anti-apoptosis marker).