1. ¹Institute of Clinical Pathology and Medical Research, Westmead Hospital, Westmead, New South Wales, Australia
2. ²The Royal Marsden NHS Trust, London, United Kingdom
3. ³Sunnybrook & Women's College Health Science Center, University of Toronto, Toronto, Canada
4. ⁴University of Tampere, Tampere, Finland
5. ⁵Pathologisches Institut der LMU Muenchen, Muenchen, Germany
6. ⁶Ciutat Santatia de Bellvitge, Barcelona, Spain
7. ⁷Centre Jean Perrin, Clermont-Ferrand, France
8. ⁸Institut für Pathologie, Kassel, Germany
9. ⁹Instituto Nazionale dei Tumori, Milano, Italy
10. ¹⁰The Netherlands Cancer Institute (MvdV), Amsterdam, The Netherlands

Correspondence: Wedad Hanna, M.D., Sunnybrook and Women's College Health Sciences Centre, Department of Anatomic Pathology, E4-36, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada; e-mail: wedad.hanna@swchsc.on.ca.

Accepted 8 November 2002.

Abstract

Knowledge of HER2 status is a prerequisite when considering a patient's eligibility for Herceptin (trastuzumab) therapy. Accurate assessment of HER2 status is essential to ensure that all patients who may benefit from Herceptin are correctly identified. There are several assays available to determine HER2 status: the most common in routine clinical practice are immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Various factors can affect the results achieved with these assays, including the assay antibody/probe, the methodology and the experience of personnel. Many countries have implemented national testing guidelines in an attempt to standardize testing procedures and make results more accurate. These guidelines vary in the level of detail and the number of recommendations. This review looks at areas of consensus between the different national testing guidelines and highlights where errors may arise during the testing procedure. The key point underlined by this review is that whatever method is used to test for HER2 status, the technology must be validated first, and there must be regular internal and external quality control and quality assurance procedures.