In all these comparisons, it is important to recall that the reference group (women with ER+PR+HER2− grade I tumours (Fig. 1g)) had an increasing mortality over follow-up (HR = 1.9, 1.4–2.7 comparing mortality at 10 vs. 1 year after diagnosis) and that ER+ high-grade tumours accounted for the largest numbers of deaths. Here, ESR1 is linked to neoplasm.