BRCA1‐deficient triple‐negative breast cancer (TNBC) presents significant treatment challenges owing to the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) targets, exhibits marked molecular heterogeneity that precludes the application of effective targeted therapies, and harbors a highly immunosuppressive tumor microenvironment. This evidence concerns the gene ESR1 and neoplasm.