Triple‐negative breast cancer (TNBC), the most aggressive subtype of breast cancer, accounts for 15%–20% of all cases and is characterized by a high propensity for invasion, metastasis, and therapeutic resistance.[1] Defined by the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), TNBC also exhibits marked intratumoral heterogeneity.[2] Although considerable progress has been made in delineating its molecular landscape, the contribution of environmental factors to TNBC progression remains poorly understood. This evidence concerns the gene ESR1 and breast cancer.