Predictive Markers of Breast Cancer: ER, PR, and HER2

Abstract

With the new role of immunohistochemistry as a test to guide the use of specific therapies, new demands for quantitative accuracy and reproducibility have been placed on laboratories. In response to this need increased quality of IHC testing, the College of American Pathologists (CAP) has released guidelines for the validation, performance, and ongoing quality management of receptor testing in breast cancer cases. This chapter reviews the new requirements of these testing guidelines to help laboratories adopt these best practices. Information is offered on the FDA approval of current antibodies for this testing. Diagrams illustrate the recommended testing algorithm combining results of immunohistochemical and in situ hybridization testing for HER2. Photomicrographs of positive, negative, and equivocal staining reactions are provided to aid in the interpretation of immunohistochemical and in situ hybridization assays. Figures demonstrating the use of appropriate and inappropriate internal control reactions serve to help decide, if results are valid and can be reported or should be rejected.