T = primary tumor; N = regional lymph node; M = distant metastasis.

^aAdapted with permission from AJCC: Breast, revised version. In: Amin MB, Edge SB, Greene FL, et al., eds.: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer, 2017, pp. 4–96.

^bT1 includes T1mi.

^cN1 does not include N1mi. T1, N1mi, M0 and T0, N1mi, M0 cancers are included for prognostic staging with T1, N0, M0 cancers of the same prognostic factor status.

^dN1 includes N1mi. T2, T3, and T4 cancers and N1mi are included for prognostic staging with T2, N1; T3, N1; and T4, N1, respectively.

Notes:

1. For cases with lymph node involvement with no evidence of primary tumor (e.g., T0, N1, etc.) or with breast ductal carcinoma in situ (e.g.,Tis, N1, etc.), the grade, human epidermal growth factor receptor 2 (HER2), estrogen receptor, and progesterone receptor information from the tumor in the lymph node should be used for assigning stage group.

2. For cases where HER2 is determined to be equivocal by in situ hybridization (fluorescence in situ hybridization or chromogenic in situ hybridization) testing under the 2013 American Society of Clinical Oncologists/College of American Pathologists HER2 testing guidelines, the HER2-negative category should be used for staging in the Pathological Prognostic Stage Group table.[4,5]

3. The prognostic value of these Prognostic Stage Groups is based on populations of persons with breast cancer that have been offered and mostly treated with appropriate endocrine and/or systemic chemotherapy (including anti–HER2 therapy).