Breast Cancer Stages

Breast cancer staging describes the extent of the disease, including the size of the tumor, and lymph node involvement, and whether breast cancer has spread to distant parts of the body (metastasis). The staging of breast cancer helps to determine the recommended treatment, along with other characteristics of cancer like hormone receptor status, human epidermal growth factor receptor 2 (HER2) status, whether the patient is postmenopausal or not, and the general health of the patient.1

Figure 1. Overview of breast cancer stages

Breast Cancer Stages

Breast cancer staging is often done according to the American Joint Committee on Cancer (AJCC) system and is based on the tumor, node, and metastasis (TNM) classification. See below for TNM classifications.

Table 1. Breast cancer classifications

Stage 0
  • Non-invasive
  • Cancer or non-cancerous abnormal cells have not moved out of the breast
Stage IA
  • Tumor is less than 20 mm
  • No lymph node involvement
Stage IB
  • No evidence of primary tumor but microscopic evidence in nearby lymph nodes, or
  • Tumor is less than 20 mm & there is microscopic evidence of breast cancer in nearby lymph nodes
Stage IIA
  • Any 1 of these conditions:
    • No evidence of primary tumor but breast cancer has spread to nearby axillary lymph nodes
    • Tumor is less than 20 mm but cancer has spread to nearby axillary lymph nodes
    • Tumor is less than 50 mm & no lymph node involvement
Stage IIB
  • Any 1 of these conditions:
    • Tumor is less than 50 mm & has spread to nearby axillary lymph nodes
    • Tumor is greater than 50 mm & no lymph node involvement
Stage IIIA
  • Any 1 of these conditions:
    • No evidence of primary tumor but cancer has spread to several axillary lymph nodes, or spread to mammary lymph node(s)
    • Tumor is less than 20 mm but cancer has spread to several axillary lymph nodes, or spread to mammary lymph node(s)
    • Tumor is less than 50 mm but cancer has spread to several axillary lymph nodes, or spread to mammary lymph node(s)
    • The tumor is larger than 50 mm in its greatest dimension & has spread to nearby axillary lymph nodes
    • The tumor is larger than 50 mm in its greatest dimension & has spread to several axillary lymph nodes, or spread to mammary lymph
Stage IIIB
  • Any 1 of these conditions:
    • Tumor has invaded the chest wall and/or has spread to the skin
    • Cancer is inflammatory breast carcinoma
Stage IIIC
  • Tumor may be any size; there is substantial lymph node involvement, with at least one area of lymph node involvement greater than 2mm
Stage IV
  • Breast cancer has spread to one or more distant areas of the body, such as the bones, liver, lungs, or brain

Additional Information can on tumor size, lymph node involvement, and metastasis can be found below:

Breast cancer tumor size

The size of the tumor is measured in millimeters and is represented by T in the TNM system.

Table 2. Tumor classifications

TX
  • Primary tumor cannot be assessed
T0
  • No evidence of primary tumor
Tis
  • Carcinoma in situ (may be ductal carcinoma in situ (DCIS), lobular carcinoma in situ(LCIS), or Paget disease)
T1a
  • The tumor is greater than 1 mm but less than or equal to 5 mm in its greatest dimension
T1b
  • The tumor is greater than 5 mm but less than or equal to 10 mm in its greatest dimension
T1c
  • The tumor is greater than 10 mm but less than or equal to 20 mm in its greatest dimension
T2
  • The tumor is greater than 20 mm but less than or equal to 50 mm in its greatest dimension
T3
  • The tumor is larger than 50 mm in its greatest dimension
T4a
  • The tumor has invaded the chest wall
T4b
  • The tumor extends to the skin (causing ulceration and/or satellite breast nodules (on the same side of the body) and/or swelling (possibly appearing as an orange peel effect of the skin, called peau d’orange), but does not meet criteria for inflammatory breast carcinoma)
T4c
  • Both T4a and T4b
T4d
  • Inflammatory breast carcinoma

Lymph node involvement

When breast cancer spreads through the lymphatic system to the lymph nodes, it can spread to the:

  • Axillary lymph nodes, which are found under the arm
  • Clavicular lymph nodes – including supraclavicular and infraclavicular – which are found above (supra-) and below (infra-) the collarbone
  • Mammary lymph nodes, which are within the breast tissue

Table 3. Lymph node classification

NX
  • The regional lymph nodes cannot be assessed
N0
  • No regional lymph nodes are involved
N1
  • The breast cancer has spread to level I, II axillary lymph node(s)on the same side of the body, and the nodes are still movable
N2a
  • The breast cancer has spread to 4-9 axillary lymph nodes, and the nodes are matted or fixed to one another or other structures nearby
N2b
  • The breast cancer has spread to at least one mammary lymph node(s), causing them to be enlarged
N3a
  • The breast cancer has spread to at least 10 axillary lymph nodes with at least one area being larger than 2 mm, or
  • The breast cancer has spread to the lymph nodes under the collarbone with at least one area being larger than 2 mm
N3b
  • The breast cancer is in at least one axillary lymph node with at least one area being larger than 2 mm and has enlarged the mammary lymph nodes, or
  • The breast cancer has spread to at least 4 axillary lymph nodes with at least one area being larger than 2 mm and tiny amounts of cancer found in mammary lymph nodes
N3c
  • The breast cancer has spread to the supraclavicular lymph nodes with at least one area being larger than 2 mm

Metastatic breast cancer

If breast cancer spreads to other organs in the body, it most commonly spreads to the bones, lungs, liver, or brain.2

Table 4. Classification of breast cancer metastasis

MX
  • Distant metastases cannot be assessed
M0
  • No distant metastases are found on imaging tests or physical exam
M1
  • The breast cancer has spread to one or more distant organs in the body

Summary of TNM classifications

Table 5. TNM classifications

Stage Tumor size (T) Node involvement (N) Metastases(M)
Stage 0 Tis N0 M0
Stage IA T1 N0 M0
Stage IB T0 N1mi M0
T1 N1mi M0
Stage IIA T0 N1 M0
T1 N1 M0
T2 N0 M0
Stage IIB T2 N1 M0
T3 N0 M0
Stage IIIA T0 N2 M0
T1 N2 M0
T2 N2 M0
T3 N1 M0
T3 N2 M0
Stage IIIB T4 N0 M0
T4 N1 M0
T4 N2 M0
Stage IIIC Any T N3 M0
Stage IV Any T Any N M1
Written by: Emily Downward | Last reviewed: December 2018.
View References
  1. Breast cancer treatment – PDQ, Stage Information. National Cancer Institute. Available at https://www.cancer.gov/types/breast/hp/breast-treatment-pdq#section/_27. Accessed 8/16/18.
  2. https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/stages-of-breast-cancer.html. Accessed 8/16/18.