[Quality control of the assay of receptors in human breast tumors].

Many technical problems are encountered when measuring estradiol and progesterone receptors in breast tumors biopsies. They are due to both intrinsic characteristics of the tissue, and to receptors instability. Suggestions are made to establish an internal quality control in each laboratory at the different steps: obtention and storage of biopsies, purity checking of the reagents, control of the assay protocol, and calculations. Several methods to prepare control pools have been proposed. They use either mammary tumors or animal target organs, and stable concentrations of receptors have been obtained by storage in liquid nitrogen or lyophilization. Published studies have demonstrated important interlaboratory variations. These discrepancies might be in part reduced by using the same assay protocol in the different participating laboratories.