The wide spread of new treatments can be seen for advanced breast cancer (ABC), with the use of cyclin-dependent kinase 4 and 6 inhibitors in hormone receptor–positive ABC [5-7] and the development of many new drugs that target human epidermal growth factor receptor 2 (HER2) [8,9], resulting in an update to the classification of HER2-positive ABC [10]. The gene discussed is CDK4; the disease is aneurysmal bone cyst.