IMMUNOHISTOCHEMICAL ASSAY FOR ESTROGEN-RECEPTORS IN PARAFFIN WAX SECTIONS OF BREAST-CARCINOMA USING A NEW MONOCLONAL-ANTIBODY

The aim of this study was to evaluate the utility of a new monoclonal antibody (AER311) that targets the oestrogen receptor (ER) in an immun ohistochemical assay (IHA) applied to breast cancers. Ninety-seven cas es of invasive ductal carcinoma were studied by AER311-IHA using a pre ssure-cooking antigen retrieval technique applied to formaldehyde-fixe d, paraffin-embedded tissue sections; immunostaining was assessed by s emi-quantitative scoring (H score). There was 80 per cent concordance between the ER status measured by dextran-coated charcoal (DCC) assay and AER311-IHA, with 63/97 (65 per cent) tumours positive and 15/97 (1 5 per cent) tumours negative by both assays. Of the 12 DCC-positive ca ses that were negative by AER311-IHA, 11 mere borderline positive (3-8 fmol/mg). Similarly, six of seven DCC-negative cases that scored posi tive by AER311-IHA had only borderline positive H scores (<50). When A ER311-IHA was compared with 1D5-IHA, there was good concordance in ER status (77 per cent) and a significant correlation (r=0.7, P<0.001) be tween H scores. Nevertheless, the correlation between ER level determi ned by AER311-IHA and that measured by DCC (r=0.53, P<0.001) was highe r than that for 1D5-IHA (r=0.32, P=0.002). AER311-IHA can therefore pr ovide reliable information about the ER status of breast carcinoma on paraffin sections and is an acceptable alternative to other commercial ly available monoclonal antibodies.