Immunohistochemical steroid receptor detection in frozen breast cancer tissue. A multicenter investigation

Now that monoclonal antibodies against the estrogen receptor (ER) have become available, it is possible to detect the presence of ER immunohistochemically. In order to evaluate the validity of the immunohistochemical (ERICA) method in a routine detection of ER, we have tested the method in a multicenter investigation. As reference is used a conventional biochemical assay, dextran-coated-charcoal assay (DCC). The investigation analyzes the validity of the ERICA-assay, including a semiquantitative estimation of the ER-content, when the method is used in several independent departments of pathology, and the interobserver variation of the analysis. The results show that the qualitative detection of ER, obtained by the ERICA-assay and the DCC-assay has a concordance of about 90% for all the participating departments. The concordance is around 60-70%, when a semiquantitative estimation of the ER-content is used. The interobserver variation is also very low, with full agreement in 58 of 59 cases. The ERICA-assay may, therefore, be a relevant alternative to the DCC-assay. However, its clinical importance still has to be fully elucidated.