MKI67 and breast cancer: There are 5 main types of breast cancer, which include luminal A (hormone receptor positive, HER-2 low expression, with low levels of Ki-67), luminal B (hormone receptor positive, either HER-2 positive or low expression, with high levels of Ki-67), HER-2 positive (hormone receptor low expression), triple negative (hormone receptor and HER-2 low expression) and finally normal breast-like (38).