The immunocytochemical versus cytosol measurement of the oestrogen receptor in invasive breast cancer tissue

Abstract To compare two methods of measurement of oestrogen receptor (ER)-expression in invasive breast cancer tissue. Sections from 299 breast cancer cases were stained for the ER by immunocytochemical assay (ICA), using mouse monoclonal antibody (MAb) NCL-ER-6SF11, and by the dextran-coated charcoal assay (DCC). Concordant results were observed in 230 of the 299 cases (77%), 69 patients had discordant results (kappa=0.537). We found a moderate concordance between ICA and DCC for ER measurement in breast cancer tissue. If we change the golden standard from DCC to ICA, 23% of patients would receive a different therapeutic approach.