Oestrogen receptor beta: how should we measure this?

Since a second oestrogen receptor (ER), ERβ was identified in the middle of the 1990s ( Mosselman et al, 1996 ), there has been much effort directed into trying to define its biological role in hormone sensitive tissue such as the mammary gland, particularly at the protein level. In a recent issue of British Journal of Cancer , Saunders et al (2002) reported immunohistochemical detection of ERβ in 51 breast tumours. In their study cohort, almost all samples were positive for ERβ (48 out of 51; 94%). In an earlier issue of British Journal of Cancer ( Skliris et al, 2001 ), we too reported immunohistochemical detection of ERβ in a similar sized cohort of 63 breast tumours, and showed much less positive nuclear ERβ immunoreactivity (48 out of 65; 74%). It is interesting to note that both studies used an identical scoring system, based on assessing both staining intensity (scored 0–3) and percentage positivity (scored 0–5), which generates a numerical score ranging from 0–8 ( Allred et al, 1998 ). In both instances, a score of >2 was considered positive.