ReviewsMolecular Prognostic and Predictive Assays in Breast Cancer A Practical ReviewLee, Ina Han MD, PhDAuthor Information From the University of Maryland Medical Center, Department of Pathology, Baltimore, MD. Reprints: Ina Han Lee, University of Maryland School of Medicine, Department of Pathology, Baltimore, MD, 22 S Greene St, Baltimore, MD 21201. E-mail: firstname.lastname@example.org. The author has no funding or conflicts to declare. AJSP: Review and Reports: January/February 2016 - Volume 21 - Issue 1 - p 4-10 doi: 10.1097/PCR.0000000000000125 Buy Metrics Abstract The last 2 decades have seen vast improvements in our understanding of breast cancer as a heterogeneous disease and in the treatment of breast cancer through targeted therapies. The risk stratification limits of current clinicopathologic and immunohistochemical parameters, however, continue to leave a significant number of patients with breast cancer at risk for overtreatment and undertreatment. This review discusses the impact of molecular studies on our current understanding of breast tumor pathogenesis and classification, recent developments in our understanding of tumor biology, new approaches to the search of new therapeutic targets, and practical insights into the validity and utility of commercially available multigene predictive molecular assays. © 2016 Lippincott Williams & Wilkins, Inc.