Human breast tumors: a comparison between the biochemical method of measuring estrogen and progesterone receptors and that of an immunohistochemical method.

In a series of 94 human mammary carcinomas, the determination of total estrogen (ER) and progesterone (PR) receptors by a single saturating dose method (5 nM for ER, 10 nM for PR) using dextran-coated charcoal was compared to an immunohistochemical method utilizing ER monoclonal antibody (ER-ICA test). There was a good correlation expressed in positive terms between the ER-ICA test and the biochemical determination of ER (94% of concordance) with a statistical value of P less than 0.01 being found between the concentration of ER (biochemical) and the percentage of labeled cells (ER-ICA). The ER-ICA test complements the ER and PR (biochemical) and is particularly useful for ER determinations on small tumor specimens as no additional tissue other than that from the biopsy is required.