Review ArticlesHER2 in Breast Cancer: A Review and UpdateKrishnamurti, Uma MD, PhD; Silverman, Jan F. MDAuthor Information Department of Pathology and Laboratory Medicine, Allegheny General Hospital, Allegheny Health Network, Pittsburgh, PA The authors have no NIH funding or conflicts of interest to disclose. Reprints: Uma Krishnamurti, MD, PhD, Department of Pathology and Laboratory Medicine, Allegheny General Hospital, Allegheny Health Network, 320 East North Ave., Pittsburgh, PA 15212 (e-mail: firstname.lastname@example.org). Advances In Anatomic Pathology: March 2014 - Volume 21 - Issue 2 - p 100-107 doi: 10.1097/PAP.0000000000000015 Buy Metrics Abstract HER2 (human epidermal growth factor receptor 2) receptor is a membrane tyrosine kinase and when activated affects cell proliferation and survival. The HER2 oncogene is located on chromosome 17q12. HER2 amplification is the primary pathway of HER2 receptor overexpression and is a major driver of tumor development and progression in a subset of breast cancers. HER2 is amplified in about 15% to 20% of breast cancers. The overexpressed HER2 receptor is a valuable therapeutic target. The 2007 ASCO guidelines mandate that HER2 should be evaluated in every invasive breast cancer, either at the time of diagnosis or recurrence to guide therapy. Currently HER2 testing is carried out by several methods. It is crucial to standardize testing techniques to accurately assess HER2 status. The aim of this review on HER2 in breast cancer is to discuss the important aspects of HER2 biology, its significance in breast cancer, and the current standards for its detection. © 2014 by Lippincott Williams & Wilkins.