Immunoperoxidase localization of estrogen receptors in human brest carcinoma.

Monoclonal antibodies to the estrogen receptor protein were used to evaluate the specificity of the peroxidase antiperoxidase (PAP) method for localization of estrogen receptors (ER) in human breast carcinoma. Twenty-five cases of breast carcinoma were selected, and they were roughly classified as ER-rich and ER-poor tumors based on ER levels as determined by dextran-coated charcoal (DCC) assay. ER-rich tumors showed strongly positive cytoplasmic and, to a lesser degree, nuclear staining. Both the cytoplasmic and nuclear staining were less intense in ER-poor tumors, and the staining intensity varied from one to another cell population in the same tumor. Completely negative cells were also observed. The results of the PAP and DCC methods correlated fairly well in ER-rich tumors but not in ER-poor tumors. The PAP method provided visual localization of ER combined with excellent tissue morphology. Application of both methods (DCC and PAP) may provide better assessment of the estrogen receptor levels in breast carcinomas.