American Joint Committee on Cancer's Staging System for Breast Cancer, Eighth Edition: Summary for Clinicians

Breast cancer is commonly staged using the American Joint Committee on Cancer (AJCC) staging system. The 7^th edition of the AJCC Staging Manual, was a purely anatomic staging method, which uses primary tumor size (T), nodal involvement (N), and metastasis (M) based on clinical and pathological evaluations. Advancements in tumor biology and prognostic biological markers, such as estrogen receptor (ER)/progesterone receptor (PR), HER2/neu, and Ki-67, have allowed clinicians to understand why similarly staged patients had significantly different outcomes. The most recent update to the staging system integrates molecular markers with disease extent for more optimal estimation of prognosis. This change improves the prognosis of breast cancer patients and better informs physicians in the planning of treatments. This review summarizes the changes in the AJCC Staging Manual, 8^th edition and their impact on practicing radiologists in breast cancer management.