ESR1 and breast cancer: Triple‐negative breast cancer (TNBC) has a higher risk of recurrence and death than other breast cancer (BC) subtypes though accounts for only 10–30% of all BC cases.[1] Due to the absence of estrogen receptor, human epithermal growth factor receptor 2, and progesterone receptor, it is unable to benefit from traditional BC targeted therapies, and thus finding out alternative targets for TNBC treatment has always been a prominent topic in BC research.