ESR1 and neoplasm: Among patients with ER positive tumours and a high expression of 17βHSD14, tamoxifen significantly reduced local recurrence rates in univariate Cox models (HR 0.38; 95% C.I. 0.19–0.77, p = 0.007) when compared to patients bearing tumours with intermediate, low or negative expression levels (HR 1.19; 95% C.I. 0.54–2.59; p = 0.66), for whom tamoxifen did not have an impact on local recurrence rates (Fig. 4, Table 3).