Targeting this pathway with cyclin-dependent kinase 4 and 6 (CDK4 and CDK6) inhibitors in combination with ET results in significant improvement in clinical outcomes over ET alone [5–15], with CDK4 and CDK6 inhibitor/ET combination therapy emerging as the new standard of care in the treatment of HR+ , HER2− advanced breast cancer (ABC) [16]. The gene discussed is ERBB2; the disease is aneurysmal bone cyst.