Staging Breast Cancer

Breast cancer staging is used to determine the extent of the disease upon diagnosis. The stage of the disease is important to develop an appropriate treatment plan and determine the prognosis (expected outcome of the disease). Physical examination, imaging tests (e.g., mammogram, ultrasound), and pathology results following biopsy or other surgery are used to stage breast cancer.

The tumor, node, metastasis (TNM) system classifies cancer by tumor size (T), the degree of regional spread or lymph node involvement (N), and distant metastasis (M). Using this system, breast cancer is assigned a stage from I to IV.

Stage 0 breast cancer sometimes is considered a pre-cancerous condition. Ductal carcinoma in situ (DCIS) is an example of stage 0 breast cancer. In DCIS, cancer cells are located within a milk duct, but have not invaded breast tissue or spread to lymph nodes or distant sites. Other types of breast cancer that may be classified as stage 0 include lobular carcinoma in situ (LCIS) and Paget disease of the nipple.

In stage I breast cancer, the tumor is 2 cm or less in diameter (T1) and cancer cells have not spread to lymph nodes (N0) or to distant sites (M0).

Stage II breast cancer is classified as stage IIA or stage IIB. A stage IIA classification involves the following:

  • no tumor is located in the breast (T0), but cancer cells are found in 1–3 axillary (under the arm) lymph nodes (N1) and have not spread to distant sites (M0); or
  • tumor is less than 2 cm in diameter (T1) and cancer cells have spread to 1–3 axillary lymph nodes (N1), but not to distant sites (M0); or
  • tumor is larger than 2 cm and less than 5 cm in diameter (T2) and cancer cells have not spread to axillary nodes (N0) or to distant sites (M0).

Stage IIB classification of breast cancer involves the following:

  • tumor is larger than 2 cm and less than 5 cm in diameter (T2) and cancer cells have spread to 1–3 axillary lymph nodes (N1), but not to distant sites (M0); or
  • tumor is larger than 5 cm and does not grow into the chest wall (T3) and cancer cells have not spread to lymph nodes (N0) or to distant sites (M0).

Breast cancer also is classified as stage IIB when sentinel node biopsy, but not imaging tests or clinical examination, shows that cancer cells have spread to internal mammary lymph nodes.

Classifications for stage III breast cancer include stage IIIA, stage IIIB, and stage IIIC. Stage IIIA involves the following:

  • tumor is less than 5 cm in diameter (T0–T2) and cancer cells have spread to 4 to 9 axillary lymph nodes (N2), but not to distant sites (M0); or
  • tumor is larger than 5 cm (T3) and cancer cells have spread to 1 to 9 axillary nodes (N0–N2) or to internal mammary nodes, but not to distant sites (M0).

In stage IIIB breast cancer, the tumor has grown into the chest wall or the skin (T4) and cancer cells may have spread to as many as 9 axillary nodes (N0–N2), but not to distant sites (M0).

Stage IIIC breast cancer involves a tumor of any size (T0–T4) and cancer cells that have spread to 10 or more axillary lymph nodes, or to 1 or more other regional lymph nodes, or to internal mammary lymph nodes (enlarging these nodes) on the same side as the tumor (N3), but not to distant sites (M0). Inflammatory breast cancer also is classified as stage III, unless it has spread to a distant site.

Stage IV breast cancer is a tumor of any size (T0-T4) and cancer cells that may have spread to nearby lymph nodes (N0-N3) and have spread to a distant site (M1). Common sites of metastasis include the bones, liver, lungs, brain, and distant lymph nodes.

Classification of Cancer has additional information about general cancer staging.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 24 Apr 2007

Last Modified: 18 May 2011