Endocrine therapy (ET) is the treatment of choice for patients with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2–) advanced breast cancer (ABC) [1]; however, resistance remains a barrier to long-term clinical benefit, which has led to the development of therapies that reverse or delay this resistance [2]. Here, ERBB2 is linked to aneurysmal bone cyst.