Elderly patients are more likely to have hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) disease compared with younger patients; in the 2010 Surveillance, Epidemiology, and End Results (SEER) registry database, 58% of patients diagnosed with HR+, HER2− breast cancer were younger than 50 years, 63% were aged 50–64 years, and 68% of patients were aged 65 years or older [2]. Here, ERBB2 is linked to breast cancer.