QUANTITATIVE IMMUNOHISTOCHEMICAL ASSAY FOR HORMONAL RECEPTORS - TECHNICAL ASPECTS AND BIOLOGICAL SIGNIFICANCE

Over 250 breast carcinomas were studied in order to establish whether or not quantitative inununohistochemical assays (ICA) for estrogen and progesterone receptors (ER and PR) with computer-assisted image analy sis could favorably compare with standard cytosolic assays. Initially, variable antigenic preservation secondary to improper tissue fixation and processing led to irregular receptor preservation and unevenly st ained areas indistinguishable from true intratumor antigenic heterogen eity. As a direct consequence of the field selections chosen for analy sis, assay reproducibility was less than optimal. Proper tissue fixati on and handling eliminated most of the irregular staining; selection o f fields to analyze became less cumbersome and more reproducible. Diff erences in staining intensity due to minimal variations in the ICA als o resulted in difficult reproducibility. Standardizing the technique a nd using an automatic stainer notably eliminated that problem. The sec ond and equally important question was to establish if quantitative ER -ICA had relevance as a predictor for prognosis. The Kaplan-Meier prod uct limit estimator for quantitated ER values and Cox regression for r isk of mortality and disease progression were performed. The results o btained discriminated high- and low-risk groups for overall survival ( p = 0.016) better than the dextran-coated charcoal assay. Elimination of two major obstacles and proof of the predictive value of quantitati ve ICA has transformed the assay into a valid alternative to cytosolic methods; however, before that takes place it is critical to establish standard procedures for both ICA and quantitation so interlaboratory variability is reduced to a minimum. (C) 1994 Wiley-Liss, Inc.