Recommendations for validating estrogen and progesterone receptor immunohistochemistry assays

Context.—Estrogen receptor and progesterone receptor status is assessed on all newly diagnosed, invasive breast carcinomas and in recurrences to determine patient eligibility for hormonal therapy, but 10% to 20% of estrogen receptor and progesterone receptor test results are discordant when tested in multiple laboratories. Objective.—To define the analytic (technical) validation requirements for estrogen receptor and progesterone receptor immunohistochemistry assays used to select patients for hormonal therapy. Data Sources.—Literature review and expert consensus. Conclusions.—A standardized process for initial test validation is described. We believe adoption of this process will improve the accuracy of hormone-receptor testing, reduce interlaboratory variation, and minimize false-positive and false-negative results. Required ongoing assay assessment procedures are also described.