MKI67 and breast cancer: There is still no unequivocal consensus on the cut-off for low or high Ki-67; but for example the European Society for Medical Oncology (ESMO) Early Breast Cancer Guidelines use a Ki-67 expression of ≥ 20% as a cut-off for high-risk disease and also for classifying luminal A-like and luminal B-like breast cancers [15].