Oestrogen receptor β: what it means for patients with breast cancer

Summary Oestrogen receptor (ER)α is a well established prognostic marker in breast cancer, and all patients who are ER α positive receive tamoxifen as adjuvant endocrine therapy. Although ERα predicts a favourable disease outcome, the usefulness of ERβ as a clinical prognostic marker remains to be defined. Here, we outline the history of both ERs and discuss the implications ERβ has to patients with breast cancer.