While TNBC does not express ERα, expression of estrogen receptor beta (ERβ) in 25%-30% of TNBC offers a promising opportunity for targeted antitumorigenic therapy.1,2 Expression of ERβ has been identified as an independent predictor of recurrence, metastasis, and mortality, and is generally regarded as a favorable clinical feature in breast cancer. This evidence concerns the gene ESR1 and breast cancer.