ERBB2 and breast carcinoma: When using the cut point of ≥20% of Ki67 stained cells, as used to predict favorable response to abemaciclib combined with endocrine therapy for the adjuvant treatment of hormone positive, HER2 negative, node-positive, high-risk, early breast cancer [25], the level of overall agreement in our EQA ring study was lower, though still relatively high with an overall agreement of 81% for Ki-67 testing.