We read with interest the paper by Borgquist et al, published recently in this journal.1 In their article, the authors aimed to investigate the impact of oestrogen receptor β (ERβ) expression on breast cancer outcome using a cohort of 512 tumours represented in tissue microarray (TMA). Since the discovery of ERβ over a decade ago, this has been the goal of many research groups. However, progress in this area has been impeded by the lack of a consensus in terms of choice of primary antibody and cut-off value used to determine ERβ positivity.2 3 Additionally, we know that ERβ exists as five isoforms (ERβ1–5), each formed by alternative splicing of the last coding exon,4 5 which …