ReviewsChanges and Clarifications in the Eighth Edition of the AJCC Cancer Staging System for Breast CancerSanders, Mary Ann MD, PhD*; Wong, Stephanie M. MD, MPH†; Iorgulescu, Julian Bryan MD‡; Lester, Susan C. MD, PhD‡Author Information From the *Department of Pathology and Laboratory Medicine, University of Louisville, Louisville, KY; †Department of Surgery, McGill University Health Centre, Montreal, Quebec, Canada; and ‡Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA. Reprints: Susan C. Lester, MD, PhD, Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St, Boston, MA 02115. E-mail: firstname.lastname@example.org. The authors have no funding or conflicts to declare. AJSP: Reviews & Reports: May/June 2018 - Volume 23 - Issue 3 - p 113-117 doi: 10.1097/PCR.0000000000000239 Buy Metrics Abstract In the eighth edition of the American Joint Committee on Cancer staging system for breast cancer, the definitions for T (tumor), N (nodes), and M (metastases) remain substantially unchanged but with clarifications for certain categories that may have been problematic for pathologists and clinicians. The principal change is the decision to exclude lobular carcinoma in situ from T classification. In contrast, there is a major change in how stage is determined by introducing a new clinical prognostic stage and a new pathological prognostic stage. These prognostic stages incorporate information about grade, estrogen receptor expression, progesterone receptor expression, human epidermal growth factor receptor 2 expression, and, in some cases, the Oncotype Dx Recurrence Score, in addition to T, N, and M, to create groups of cancers predicted to have a similar survival at 3 years based on information from the National Cancer Database. This review highlights the changes and notable clarifications to the TNM system and how these relate to standard pathology reporting. © 2018 Lippincott Williams & Wilkins, Inc.