ESR1 and aneurysmal bone cyst: Finally, biomarker-driven clinical trials evaluating dinaciclib and palbociclib combined with ET in ER+/HER2- postmenopausal ABC patients who progressed on AI, and also in patients who progressed on combined palbociclib and fulvestrant, eligible by evaluation of the expression of the three biomarkers in baseline biopsy specimens, may ultimately determine the utility of the combined biomarker.