Palbociclib, a CDK4/6 inhibitor, has been reported to significantly prolong progression-free survival (PFS) in hormone receptor (HR)-positive/HER2-negative advanced breast cancer (ABC) when combined with aromatase inhibitors or fulvestrant, compared with aromatase inhibitors or fulvestrant alone [4-6]. The gene discussed is ERBB2; the disease is aneurysmal bone cyst.