This paradox, as well as inherent differences in biology between ER+ and ER- disease, may also contribute to the conflicting findings in ER+ and ER- breast cancer, although further study is needed to provide larger sample sizes as the discovery cohort used in this study is underpowered to assess this fully and so we cannot rule out an association between pnSTING and outcome in ER- disease. Here, ESR1 is linked to breast cancer.