HR and breast cancer: A panelof immunohistochemistry (IHC) biomarkers can classify breast cancer into four surrogatesubtypes: hormone receptors (HR) (estrogen (ER) and progesterone (PR)), HER2 and Ki67.These classify luminal A-like (low Ki67, HR+ , HER2−), luminal B-like (high Ki67, HR+ ,HER2−), HER2 positive (HER2+) and triple negative (HR−, HER2−) tumors [3, 4].