ESR1 and breast cancer: Our results show that GREB1 mRNA is highly expressed in breast carcinomas than normal breast tissues (T-test: 4.815; P-value: 2.1E-5), GREB1 mRNA is significantly overexpressed in ER-positive breast cancer patients compared to that of ER-negative patients (Figure 2) [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46], [47].