For ER-positive, HER2-positive ABC, the current first-line standard consists of trastuzumab, pertuzumab, and docetaxel, as demonstrated in the CLEOPATRA study (ORR 80.2%; median PFS 18.7 months) [27,28] and confirmed by the PUFFIN trial conducted in China (ORR 79%; median PFS 16.5 months) [3,29]. The gene discussed is ERBB2; the disease is aneurysmal bone cyst.