Breast Cancer Stages

After a breast cancer diagnosis, the oncologist will need to determine if cancer cells have spread outside of the breast. Staging can sometimes take a little while to determine because results need to be gathered from different types of tests. One of these tests may be available after surgery when nearby lymph nodes are examined to see if cancer cells have spread there.

In breast cancer, stage is based on several factors:

1. The size and location of the primary tumor
2. Whether the cancer of the breast has spread to nearby lymph nodes or other parts of the body
3. Tumor grade
4. The presence of certain biomarkers.

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TNM System

The first two items on the list are determined using the TNM system. TNM stands for:

• T = Tumor size
• N = Lymph Node status (the number and location of lymph nodes with cancer)
• M = Metastases (whether or not 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 disease of the breast with no associated tumor mass)
• T1: The tumor is 20 millimeters or smaller. There are 4 subtypes of a T1 tumor depending on the size of the tumor:
  • T1mi: the tumor is 1 millimeter or smaller.
  • T1a: the tumor is larger than 1 millimeter but not larger than 5 millimeters.
  • T1b: the tumor is larger than 5 millimeters but not larger than 10 millimeters.
  • T1c: the tumor is larger than 10 millimeters but not larger than 20 millimeters.
• T2: The tumor is larger than 20 millimeters but not larger than 50 millimeters.
• T3: The tumor is larger than 50 millimeters.
• T4: The tumor is described as one of the following:
  • T4a: the tumor has grown into the chest wall 
  • T4b: the 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: the 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 1 to 3 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 1 to 3 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 4 to 9 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 1 to 9 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 4 to 9 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. If cancer has spread to distant lymph nodes, the cancer in the lymph nodes is larger than 0.2 millimeters. The cancer is called metastatic breast cancer.

Breast Cancer by Stage

The following grouping by T, N and M according to stage is provided by the American Society of Clinical Oncology.

Stage 0 Also called non-invasive. Disease that is only in the ducts of the breast tissue and has not spread to the surrounding tissue of the breast.	Tis Ta	N0	M0
Stage IA The tumor is small, invasive, and has not spread to the lymph nodes	T1	N0	M0
Stage IB Cancer has spread to the lymph nodes and the cancer in the lymph node is larger than 0.2 mm but less than 2 mm in size. There is either no evidence of a tumor in the breast or the tumor in the breast is 20 mm or smaller	T1 or T2	N1	M0
Stage IIA Any 1 of these conditions:   There is no evidence of a tumor in the breast, but the cancer has spread to 1 to 3 axillary lymph nodes. It has not spread to distant parts of the body.  The tumor is 20 mm or smaller and has spread to the axillary lymph nodes. The tumor is larger than 20 mm but not larger than 50 mm and has not spread to the axillary lymph nodes.	T0   T1   T2	N1   N1   N0	M0   M0   M0
Stage IIB Either of these conditions:   The tumor is larger than 20 mm but not larger than 50 mm and has spread to 1 to 3 axillary lymph nodes. The tumor is larger than 50 mm but has not spread to the axillary lymph nodes.	T2   T3	N1   N0	M0   M0
Stage IIIA Either of these conditions: The cancer of any size has spread to 4 to 9 axillary lymph nodes or to internal mammary lymph nodes. It has not spread to other parts of the body  A tumor larger than 50 mm that has spread to 1 to 3 axillary lymph nodes	T0, T1, T2 or T3   T3	N2   N1	M0   M0
Stage IIIB The tumor has spread to the chest wall or caused swelling or ulceration of the breast or is diagnosed as inflammatory breast cancer. It may or may not have spread to up to 9 axillary or internal mammary lymph nodes. It has not spread to other parts of the body.	T4	N0, N1 or N2	M0
Stage IIIC A tumor of any size that has spread to 10 or more axillary lymph nodes, the internal mammary lymph nodes, and/or the lymph nodes under the collarbone. It has not spread to other parts of the body.	Any T	N3	M0
Stage IV Also called metastatic breast cancer. The tumor can be any size and has spread to other organs, such as the bones, lungs, brain, liver, distant lymph nodes, or chest wall.	Any T	Any N	M1
Recurrent Recurrent cancer is cancer that has come back after treatment, and can be described as local, regional, and/or distant. If the cancer does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis.

Breast Cancer Tumor Grade

The tumor’s grade is a measurement of how much the cancer cells look like normal cells. This will give the oncologist a better idea of how quickly the cancer is likely to grow and spread.

To describe how abnormal the cancer cells and tissue are, the pathologist will assess the following three features:

1. How much of the tumor tissue has normal breast ducts.
2. The size and shape of the nuclei in the tumor cells.
3. How many dividing cells are present, which is a measure of how fast the tumor cells are growing and dividing.

For each feature, the pathologist assigns a score of 1 to 3; a score of “1” means the cells and tumor tissue look the most like normal cells and tissue, and a score of “3” means the cells and tissue look the most abnormal. The scores for each feature are added together to get a total score between 3 and 9.

Three grades of breast cancer are possible:

• Total score of 3 to 5: G1 (Low grade or well-differentiated).
• Total score of 6 to 7: G2 (Intermediate grade or moderately differentiated).
• Total score of 8 to 9: G3 (High grade or poorly differentiated).

Biomarkers

Healthy breast cells, and some breast cancer cells, have receptors (biomarkers) 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, progesterone or HER2 receptors. 

The results of the testing will produce a positive (+) or negative (-) for each biomarker as part of the diagnosis. For some patients there are no biomarkers present. This will be classified as triple-negative breast cancer. 

The combination of all these factors result in a best recommendation for breast cancer treatment.