ERBB2 and breast cancer: Interestingly, the American Food and Drug Administration (FDA) has recently approved abemaciclib, a CDK4/6 inhibitor, in combination with endocrine therapy in the adjuvant setting for HR+/HER2- and node-positive BC at high risk for recurrence with a Ki67 proliferative index of ≥20% (immunohistochemistry validated on Agilent platforms with the MIB1 clone).