However, a significant proportion of patients develop secondary resistance to hormonal treatments, particularly being identified as an important molecular mechanism of acquired resistance in hormone receptor-positive/human epidermal growth factor receptor 2-negative breast cancer (HR+/HER2- BC) patients after the first line of endocrine therapy (ET) [[1], [2], [3], [4], [5], [6]]. The gene discussed is ERBB2; the disease is breast cancer.