Prognostic significance of oestrogen receptor β in breast cancer

Background: Endocrine therapy for breast cancer is now well established and with the identification of a second oestrogen receptor, ER beta, 3 years ago it is timely to review the possible significance of this receptor in breast cancer management. Methods: An up-to-date review of the current literature concerning the role and possible implications of ER beta in human breast cancer was undertaken. Results: Wild-type and variant ER beta are expressed in human breast tumours. Expression of ER beta correlates with accepted prognostic indicators including lymph node status and tumour grade. Furthermore, levels of ER beta messenger RNA alter during carcinogenesis and are upregulated in breast tumours that develop antioestrogen resistance. Conclusion: ER beta has potential as a novel clinical prognostic marker in breast cancer, particularly in determining tumours that are resistant to tamoxifen.