In the past few years, the CDK4/6 inhibitors palbociclib, ribociclib, and abemaciclib have been approved and recommended [53] for the treatment of hormone-receptor-positive, HER2-negative aBC on the basis of three large phase III trial programs, PALOMA, MONALEESA, and MONARCH, since all trials show a significant improvement in PFS when combined with an AI or fulvestrant [65,66,67,68,69,70,71] (Table 1). This evidence concerns the gene NR4A1 and aneurysmal bone cyst.