Both the TNBC lines had a significantly higher expression of full-length ESR2 compared with MCF10A (MDA-MB-231: 4.4-fold, p < 0.05; MDA-MB-468: 5.2-fold, p < 0.01), and these levels were comparable to those in the ERα+ MCF7 and T47D breast cancer cell lines. Here, ESR2 is linked to breast carcinoma.