Virginia Commonwealth University Breast Imaging

Women looking at a map.

Breast Cancer Staging

The American Joint Committee on Cancer (AJCC) TNM System

The TNM system described by the American Joint Committee on Cancer (AJCC) is the staging system most commonly used by the interdisciplinary team.

Clinical staging is based on the results of physical examination, imaging tests and biopsy. Pathologic staging adds the results of the microscopic evaluation of tissue removed from the breast and lymph nodes samples from underneath the arm at the time of surgery.

The TNM staging system classifies cancers based on the T, N, and M stages:

T stands for tumor

N stands for spread to lymph nodes

M is for metastasis (spread to distant organs).

Letters or numbers that appear after the T, N, and M provide more details on the tumor, lymph nodes, and metastasis.

Primary tumor (T)

TX: Primary tumor cannot be assessed.

T0: No evidence of primary tumor.

Tis: Carcinoma in situ (DCIS, LCIS, or Paget disease of the nipple with no associated tumor mass)

T1: Tumor is 2 cm (3/4 of an inch) or less across.

T2: Tumor is more than 2 cm but not more than 5 cm (2 inches) across.

T3: Tumor is more than 5 cm across.

T4: Tumor of any size growing into the chest wall or skin. This includes inflammatory breast cancer.

Nearby lymph nodes (N) – based on looking at them under a microscope

NX: Nearby lymph nodes cannot be assessed (previously removed).

N0: Cancer has not spread to nearby lymph nodes.

N1: Cancer has spread to 1 to 3 axillary (underarm) lymph node(s), and/or tiny amounts of cancer are found in internal mammary lymph nodes (those near the breast bone) on sentinel lymph node biopsy.

N2: Cancer has spread to 4 to 9 axillary lymph nodes under the arm, or cancer has enlarged the internal mammary lymph nodes.

N3: One of the following applies:

  • Cancer has spread to 10 or more axillary lymph nodes.
  • Cancer has spread to the lymph nodes under the clavicle (collar bone).
  • Cancer has spread to the lymph nodes above the clavicle.
  • Cancer involves axillary lymph nodes and has enlarged the internal mammary lymph nodes.
  • Cancer involves 4 or more axillary lymph nodes, and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.

Metastasis (M)

MX: Presence of distant spread (metastasis) cannot be assessed.

M0: No distant spread.

M1: Spread to distant organs is present. (The most common sites are bone, lung, brain, and liver.)

Breast cancer stage grouping

Once the T, N, and M categories are determined, the information is combined in a process called stage grouping. Cancers with similar stages tend to have a similar outlook and thus are often treated in a similar way. Stage is expressed in Roman numerals from stage I (the least advanced stage) to stage IV (the most advanced stage). Non-invasive cancer is listed as stage 0.

Stage 0: Tis, N0, M0: This is ductal carcinoma in situ (DCIS), the earliest form of breast cancer. In DCIS, cancer cells are still within a duct and have not invaded deeper into the surrounding breast tissue. Lobular carcinoma in situ (LCIS) is sometimes classified as stage 0 breast cancer, but most oncologists believe it is not a true breast cancer. In LCIS, abnormal cells grow within the lobules or milk-producing glands, but they do not penetrate through the wall of these lobules. Paget disease of the nipple (without an underlying tumor mass) is also stage 0. In all cases the cancer has not spread to lymph nodes or distant sites.

Stage I: T1, N0, M0: The tumor is 2 cm (about 3/4 of an inch) or less across and has not spread to lymph nodes or distant sites.

Stage IIA: T0, N1, M0/T1, N1, M0/T2, N0, M0: One of the following applies:

  • The tumor is 2 cm or less across (or is not found) and has spread to 1 to 3 axillary lymph nodes.
  • The tumor is 2 cm or less across (or is not found) and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.
  • The tumor is 2 cm or less across (or is not found), has spread to 1 to 3 axillary lymph nodes, and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.
  • The tumor is larger than 2 cm across and less than 5 cm but hasn’t spread to the lymph nodes.

The cancer hasn’t spread to distant sites.

Stage IIB: T2, N1, M0/T3, N0, M0: One of the following applies:

  • The tumor is larger than 2 cm and less than 5 cm across. It has spread to 1 to 3 axillary lymph nodes and/or tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.
  • The tumor is larger than 5 cm across but does not grow into the chest wall or skin and has not spread to lymph nodes.

The cancer hasn’t spread to distant sites.

Stage IIIA: T0-2, N2, M0/T3, N1-2, M0: One of the following applies:

  • The tumor is not more than 5 cm across (or cannot be found). It has spread to 4 to 9 axillary lymph nodes, or it has enlarged the internal mammary lymph nodes.
  • The tumor is larger than 5 cm across but does not grow into the chest wall or skin. It has spread to 1 to 9 axillary nodes, or to internal mammary nodes.

The cancer hasn’t spread to distant sites.

Stage IIIB: T4, N0-2, M0: The tumor has grown into the chest wall or skin, and one of the following applies:

  • It has not spread to the lymph nodes.
  • It has spread to 1 to 3 axillary lymph nodes and/or tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.
  • It has spread to 4 to 9 axillary lymph nodes, or it has enlarged the internal mammary lymph nodes.

The cancer hasn’t spread to distant sites.

Inflammatory breast cancer is classified as stage IIIB unless it has spread to distant lymph nodes or organs, in which case it would be stage IV.

Stage IIIC: T0-4, N3, M0: The tumor is any size (or can’t be found), and one of the following applies:

  • Cancer has spread to 10 or more axillary lymph nodes.
  • Cancer has spread to the lymph nodes under the clavicle (collar bone).
  • Cancer has spread to the lymph nodes above the clavicle.
  • Cancer involves axillary lymph nodes and has enlarged the internal mammary lymph nodes.
  • Cancer has spread to 4 or more axillary lymph nodes, and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.

The cancer hasn’t spread to distant sites.

Stage IV: T0-4, N0-3, M1: The cancer can be any size and may or may not have spread to nearby lymph nodes. It has spread to distant organs (the most common sites are the bone, liver, brain, or lung), or to lymph nodes far from the breast.

Virginia Commonwealth University Medical Center VCU Breast Imaging