At the end of 2016, the American Joint Committee on Cancer (AJCC) Cancer Staging Manual (8th edition) was published. The anatomic and prognostic stage groups were defined in the section on breast cancer. In the prognostic stage group, the stages were identified by using T, N, and M, as well as ER, PR, HER2, and tumor-grade biomarkers. In addition, patients in T1-2, N0, M0, grades 1-3 and those with ER (+), HER2 (-), and Oncotype DX recurrence score <11 were classified as stage IA. A year later, in the light of new data, the breast cancer section of the AJCC manual (8th edition) was updated. This review aims to reveal the changes in the stages of our institutional breast cancer patients according to the first and updated versions of the AJCC manual (8th edition) and to compare the clinical reflections with the help of staging studies with regard to the manual. According to the pathological prognostic stage data, patients mostly display downstaging.