ESR1 and triple-negative breast carcinoma: The estrogen receptor (ER) negative BCa, particular the triple negative breast cancer (TNBC) which refers to any BCa that does not express the genes for estrogen receptor (ER), progesterone receptor (PR) or Human Epidermal Growth Factor Receptor 2 (HER-2/neu), has more aggressive clinical course and less effective treatments due to lack of specific targets.