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Competing Interests: Competing interests: None declared.

A monoclonal antibody (anti-estrogen receptor [ER] from the ER-immunocytochemical assay [ICA] [Abbott Laboratories, Berkshire, England]), which binds to epitopes of the estrogen receptor in surgical biopsy specimens of breast carcinomas, was used in an improved alkaline phosphatase anti-alkaline phosphatase (APAAP) technique for in-situ receptor detection. This method was compared with a standard radioligand binding biochemical assay in assessing the ER status of 48 human breast carcinomas. The monoclonal antibody allowed detection of ER in the presence of estrogens or anti-estrogens and avoided problems of nonspecific intrinsic reactions, due to endogenous steroid hormones. The immunohistologic results (positive and negative) correlated well with the radioligand binding results (rs = 0.760; P less than 0.001) and allowed the additional assessment of cell morphology and tumor heterogeneity in the cryostat sections. The APAAP method provides diagnostic rapidity (approximately 4 hours) combined with sensitivity as compared with the radioligand assay (an approximately 2-day assay). The vivid red color associated with APAAP staining also was a distinct advantage compared with the brown reaction product of ER-ICA in interpreting stained sections. The results of this study indicate that the APAAP technique is an improved method for detection of ER and is applicable in routine hospital practice, thereby contributing to the immediate clinical management of patients with breast tumors.

A new mouse anti-oestrogen receptor (ER) monoclonal antibody, ER-P31, has been developed. Comparisons of immunohistochemical detection of ER in human breast cancers using ER-P31 with anti-ER from ER-immunocytochemical assay (ER-ICA; Abbott Diagnostic Division) and radioligand dextran-coated charcoal (DCC) assays were carried out. A total of 63 breast cancers, both ER-negative and -positive, were tested. A highly significant degree of correlation between immunostaining for ER-P31 and both ER-ICA and DCC assays was obtained. It is hoped that once ER-P31 is widely available commercially, determination of ER status in breast cancers should be routinely and economically available to all women with breast cancer. Moreover, with the introduction and implemention of a screening programme for detecting breast cancers, immunocytochemical determination of ER status in unequivocal and equivocal positive fine-needle aspirates of breast lesions can be readily performed. Copyright © 1991 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]