A comparison of three different methods for the determination of estrogen receptors in human breast cancer.

Forty-seven cases of breast cancer were analyzed for estrogen receptors (ERs) by three different techniques: (1) a biochemical assay using isoelectric focusing in polyacrylamide gel; (2) a monoclonal ER immunocytochemical assay (ERICA, Abbott Laboratories Diagnostics Division), and (3) a polyclonal antiestradiol immunohistochemical technique using formalin-fixed tissue. A high level of agreement (85%) was noted between the biochemical assay and ERICA. The ERICA-processed slides showed minimal background staining and were easy to interpret. Compared with the biochemical assay, ERICA achieved a positive predictive value of 86% and a negative predictive value of 82%. In contrast, results from the polyclonal antiestradiol histologic technique did not correlate with biochemical results and showed positive and negative predictive values of 61% and 25%, respectively. The authors conclude that the ERICA technique should prove to be a valuable adjunct to traditional biochemical ER assays.