Breast cancer is one of the most commonly diagnosed cancers in women worldwide.1 It can be divided into four intrinsic molecular subtypes including luminal A, luminal B, human epidermal growth factor receptor-2 (HER2)-enriched and triple negative by immunohistochemical analyses of estrogen receptor, progesterone receptor and HER2.2 Recurrence and metastasis are the main causes of fatality associated with breast cancer.3 Therefore, there is a desperate need to reveal the mechanisms underlying breast cancer metastasis. Here, ESR1 is linked to breast cancer.