Comparison of immunocytochemical and steroid-binding assays for estrogen receptor in human breast tumors

An estrogen receptor immunocytochemical assay which uses monoclonal antibodies to the estrogen receptor protein [Nature (Lond.), 307: 745-747, 1984] was applied to several human tissues, including human breast tumors, and the results were compared to those of steroid-binding assays performed on cytosol extracts of the same tissues. Specific immunoperoxidase staining in fixed, frozen sections was confined to the nucleus of selected cell populations within each tissue examined. In 117 human breast cancers, the presence or absence of nuclear staining was significantly associated with the concentration of cytosolic estrogen receptor. Thirty-eight estrogen receptor immunocytochemical assay-positive tumors were further assessed for several quantifiable features of the staining, including intensity, cellularity, and the proportion of tumor cells stained. Of these, epithelial cellularity showed the highest degree of correlation with the results of steroid-binding assays.