MKI67 and breast cancer: According to the St Gallen International Breast Cancer Conference in 2011, there are four breast cancer intrinsic subtypes based on the surrogate markers; Oestrogen receptor (ER), Progesterone receptor (PR), Human Epidermal receptor status and Ki-67, they include luminal A (ER+ and/or PR+, Ki67 low and HER2-), luminal B (ER+ and/or PR+, Ki67 high and/or HER2+), HER2-positive (ER-, PR- and HER2+) and triple-negative (ER-, PR- and HER2-).