ESR1 and cancer: Differentially expressed genes between the 30 ER-positive and 16 ER-negative cancers were assessed and, as shown, all the three ESR1 probes were classified as highly expressed in ER-positive cancers and were significant on multiple testing (FDR p ≤ 0.001) (Table 3) (Additional files 4, 5, 6, 7).