Testing for HER2 in Breast Cancer: Current Pathology Challenges Faced in Canada

This review is designed to highlight several key challenges in the diagnosis of human epidermal growth factor receptor 2 (HER2)–positive breast cancer currently faced by pathologists in Canada: (1) Pre-analysis issues affecting the accuracy of HER2 testing in non-excision sample types: core-needle biopsies, effusion samples, fine-needle aspirates, and bone metastases (2) HER2 testing of core-needle biopsies compared with surgical specimens (3) Criteria for retesting HER2 status upon disease recurrence. Literature searches for each topic were carried out using the MEDLINE, Embase, International Pharmaceutical Abstracts, and biosis databases. In addition, the congress databases of the American Society of Clinical Oncology (2005–2011) and the San Antonio Breast Cancer Symposium (2007–2011) were searched for relevant abstracts. All authors are expert breast pathologists with extensive experience of HER2 testing, and several participated in the development of Canadian HER2 testing guidelines. For each topic, the authors present an evaluation of the current data available for the guidance of pathology practice, with recommendations for the optimization or improvement of HER2 testing practice.