An approach to preliminary studies of interlaboratory comparative results for estrogen and progesterone receptors

Determining estrogen and progesterone (ER/PR) expression has clinical relevance in managing invasive breast carcinoma. Recent studies employing multivariate analyses which control for multiple factors have generally reaffirmed the role of ER and PR as prognostic determinants and management tools. Little information is available regarding the interlaboratory reproducibility of such testing in the clinical setting. Although ER/PR techniques based on cellular extracts have usually been used to make receptor determinations, immunohistological assays are gaining increasingly wider acceptance. The frequent admixture of non-neoplastic mammary parenchyma in tissue selected for ER and PR studies can yield false-positive results when using the cellular extraction assays, but are easily recognized with an immunohistological approach. Furthermore, specimen economy is preserved--particularly when formalin-fixed, paraffin-embedded material is used for the immunohistological assay, an important issue as more small tumors are excised. The College of American Pathologists Cell Markers Resource Committee provides clinical laboratory professionals an opportunity to compare results with peers and to participate in an immunohistology education program. Designing such a program for ER and PR immunohistological assays is presented.