breast cancer staging

After a breast cancer diagnosis is made, your oncologist will be able to tell you your clinical stage. The stage tells us how advanced the cancer appears to be. The stage of breast cancer ranges from 0 (very early) to 4 (which is cancer that has spread to other parts of the body, beyond the breast and lymph nodes). Staging is an important factor in determining prognosis as, typically, the earlier the stage, the better the outcomes. There are two staging categories: clinical stage and pathologic stage.

The clinical stage is what we believe the stage is before any surgery is performed. This is based on results from imaging studies and many different tumor factors.

The pathologic stage is determined after surgery has been performed and we know the exact size of the tumor and if any lymph nodes contain cancer.

In breast cancer, stage is based on several factors:

  1. The size of the cancer.
  2. If cancer has spread to nearby lymph nodes (or other parts of the body).
  3. Tumor grade.
  4. Receptor status (also called biomarkers). The biomarkers we test for are estrogen (ER), progesterone (PR), and HER2.

We understand the complexity of the staging diagnosis for women and men. Rest assured, your breast surgeon will explain your clinical stage in detail and answer all of your questions.

TNM System

TNM stands for:

  • T = Tumor size
  • N = Lymph Node status (the number and location of lymph nodes with cancer)
  • M = Metastases (whether the cancer has spread to other parts of the body)

T Categories for Breast Cancer

T followed by a number from 0 to 4 describes the main (primary) tumor’s size and if it has spread to the skin or to the chest wall under the breast. Higher T numbers mean a larger tumor and/or wider spread to tissues near the breast.

  • TX: Primary tumor cannot be assessed
  • T0: No sign of primary tumor
    • Tis: Carcinoma in situ (DCIS, or Paget’s disease of the breast with no associated tumor mass)
  • T1: Tumor is 20 millimeters or smaller. There are four subtypes of a T1 tumor depending on the size of the tumor:
    • T1mi: Tumor is 1 millimeter or smaller
    • T1a: Tumor is larger than 1 millimeter but not larger than 5 millimeters
    • T1b: Tumor is larger than 5 millimeters but not larger than 10 millimeters
    • T1c: Tumor is larger than 10 millimeters but not larger than 20 millimeters
  • T2: Tumor is larger than 20 millimeters but not larger than 50 millimeters
  • T3: Tumor is larger than 50 millimeters
  • T4: Tumor is described as one of the following:
    • T4a: Tumor has grown into the chest wall
    • T4b: Tumor has grown into the skin—an ulcer has formed on the surface of the skin on the breast, small tumor nodules have formed in the same breast as the primary tumor, and/or there is swelling of the skin on the breast
    • T4c: Tumor has grown into the chest wall and the skin
    • T4d: inflammatory breast cancer—one-third or more of the skin on the breast is red and swollen (called peau d’orange)

N Categories for Breast Cancer

N followed by a number from 0 to 3 indicates whether the cancer has spread to lymph nodes near the breast and, if so, how many lymph nodes are involved.

  • NX: The lymph nodes cannot be assessed
  • N0: No sign of cancer in the lymph nodes, or tiny clusters of cancer cells not larger than 0.2 millimeters in the lymph nodes
  • N1: Cancer is described as one of the following:
    • N1mi: Cancer has spread to the axillary (armpit area) lymph nodes and is larger than 0.2 millimeters but not larger than 2 millimeters
    • N1a: Cancer has spread to one-to-three axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters
    • N1b: Cancer has spread to lymph nodes near the breastbone on the same side of the body as the primary tumor, and the cancer is larger than 0.2 millimeters and is found by sentinel lymph node biopsy. Cancer is not found in the axillary lymph nodes.
    • N1c: Cancer has spread to one-to-three axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters. Cancer is also found by sentinel lymph node biopsy in the lymph nodes near the breastbone on the same side of the body as the primary tumor.
  • N2: Cancer is described as one of the following:
    • N2a: Cancer has spread to four-to-nine axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters
    • N2b: Cancer has spread to lymph nodes near the breastbone and the cancer is found by imaging tests. Cancer is not found in the axillary lymph nodes by sentinel lymph node biopsy or lymph node dissection.
  • N3: Cancer is described as one of the following:
    • N3a: Cancer has spread to 10 or more axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters, or cancer has spread to lymph nodes below the collarbone
    • N3b: Cancer has spread to one-to-nine axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters. Cancer has also spread to lymph nodes near the breastbone and the cancer is found by imaging tests
      OR
      cancer has spread to four-to-nine axillary lymph nodes and cancer in at least one of the lymph nodes is larger than 2 millimeters. Cancer has also spread to lymph nodes near the breastbone on the same side of the body as the primary tumor, and the cancer is larger than 0.2 millimeters and is found by sentinel lymph node biopsy.
    • N3c: Cancer has spread to lymph nodes above the collarbone on the same side of the body as the primary tumor

M Categories for Breast Cancer

  • M0: There is no sign that cancer has spread to other parts of the body.
  • M1: Cancer has spread to other parts of the body, most often the bones, lungs, liver, or brain. The cancer is called metastatic breast cancer.

Breast Cancer Tumor Grade

A pathologist uses tumor grade to classify tumors based on how abnormal the cancer cells look under a microscope. The grade can range from 1 to 3:

  • Grade 1 (or low grade): The cancer cells only look slightly different compared to normal, healthy cells. They tend to grow slowly.
  • Grade 2 (or intermediate/moderate grade): The cells look more abnormal, and they are growing at a faster rate.
  • Grade 3 (or high grade): The cancer cells look very abnormal and grow quickly in irregular patterns.

Remember the grade is not the same thing as the stage.

Biomarkers

Healthy breast cells, and some breast cancer cells, have receptors that attach to the hormones estrogen and progesterone. These hormones are needed for healthy cells, and some breast cancer cells, to grow and divide. To check for these biomarkers, samples of tissue containing breast cancer cells are removed during a biopsy or surgery. The samples are tested in a laboratory to see whether the breast cancer cells have estrogen (ER), progesterone (PR), and/or HER2 receptors.

The results of the testing will be reported as a positive (+) or negative (-) for each biomarker. This essentially tells us what is “feeding” the breast cancer. The results of this testing are important because this helps your doctor determine the types of treatment that your cancer is likely to respond to (such as hormone-blocking medications and/or chemotherapy).

Different types of cancer include:

  • Hormone-positive breast cancer: This is breast cancer that is estrogen and/or progesterone positive. This is the most common type of breast cancer. Part of the treatment for these cancers is a hormone-blocking pill, also called endocrine therapy (hormone therapy).
  • Triple-negative breast cancer: This is when no biomarkers are present, meaning that estrogen, progesterone, and HER2 are all negative. Since they are hormone negative, hormone-blocking medications will not be effective.
  • HER2-positive breast cancer: HER2 (human epidermal growth factor receptor 2) is a protein that may be found on the surface of some breast cancer cells. About one in five women with breast cancer have HER2-positive breast cancer. HER2-positive breast cancers tend to grow faster and are more likely to spread compared to HER2-negative breast cancers; however, there are very effective medications (immunotherapy) that can be used to specifically target HER2.
    There are 2 types of testing for HER2:
    • IHC (immunohistochemistry): This is the first test that is done to test for HER2. It uses a dye to stain for the HER2 protein. The IHC score can be 0 to 3+.
      • If 0 or 1+: HER2 negative
      • If 2+: HER2 equivocal (or borderline)
      • If 3+: HER2 positive
    • FISH (Fluorescence in situ hybridization): This is a specialized test that takes longer to get results. If the IHC testing is equivocal (borderline), then FISH testing will be done to confirm if the cancer is HER2 positive or negative.