A strongly metastatic and aggressive form of BCa is the triple-negative breast cancer (TNBC), where genes for the estrogen receptor (ER) and progesterone receptor (PR) are not expressed, and there is no amplification of the human epidermal growth factor receptor 2 (HER2) (Perou et al., 2000; Lee and Djamgoz, 2018). The gene discussed is ESR1; the disease is triple-negative breast carcinoma.