Breast cancer staging
The standard way to stage breast cancer is known as pathologic staging. It is based on the study of tumor tissue and the lymph nodes (removed during the surgery) by the pathologists.
Sometimes, the tests done during the diagnosis of breast cancer such as physical exam or tests such as mammography may help with staging the breast cancer.
Read about breast cancer basics.
The TNM system of staging
The most widely used method of staging breast cancer is the TNM system.
TNM stands for:
T = Tumor size
N = Lymph Node status (the number and location of the cancerous lymph nodes)
M = Metastases (whether or not breast cancer has spread to other areas of the body – called metastatic breast cancer)
More details on each part of the staging system are given below:
T category
The T (size) category describes the original (primary) breast tumor. The “T” with a letter or number (0 to 4) is used to describe the size and location of the tumor.
TX – the tumor can’t be assessed.
T0 – there isn’t any evidence of the primary tumor.
Tis – the cancer is “in situ” (the tumor has not started growing into healthy breast tissue).
T1, T2, T3, T4 – these signify the size of the breast tumor and the extent to which it has grown into neighboring breast tissue. The higher the T number, the larger the tumor and the more it may have grown into the breast tissue.
N category
The N (lymph node involvement) category describes whether or not cancer has reached nearby lymph nodes:
NX – the nearby lymph nodes can’t be assessed (in case if they were previously removed).
N0 – nearby lymph nodes do not contain cancer.
N1, N2, N3 – these signify the number of lymph nodes involved and how much cancer is found in them. A higher number of N signifies that higher number of lymph nodes are involved.
M category
The M (metastasis) category tells whether or not cancer has traveled to other parts of the body.
MX – metastasis can’t be assessed.
M0 – there is no distant metastasis.
M1 – distant metastasis is present.
New measures added to the staging method
Until 2018, a breast tumor stage was classified with the above mentioned three measures only. But now, the TNM system has added more below-mentioned measures:
- Tumor grade (the percentage of cancer cells that look like normal cells)
- Estrogen receptor status (do the cancer cells have receptors for the hormones estrogen?)
- Progesterone receptor status (do the cancer cells have receptors for the hormones progesterone?)
- HER2 status (are the cancer cells making too much of the HER2 protein?)
Reason for the addition of new measures to the staging system
The new measures were added because of the advantages they provide such as:
- They give specific information on the biology of the breast tumor that affects prognosis.
- Addition of these measures improves staging and gives a better understanding of the breast tumor at various stages.
For example, based on the biological measures, a large breast tumor may also have a better prognosis than a small tumor and a small tumor may have a worse prognosis than a large tumor.
Read also: Mastectomy: Procedure, Complications, Recovery, Reconstruction, Scars
Breast Pain: What Does It Indicate? Is it a Breast Cancer Sign?
Different stages of breast cancer
A breast cancer has five different stages which are explained below:
Stage 0 breast cancer
Stage zero breast cancer is used to describe non-invasive breast cancers, such as DCIS (ductal carcinoma in situ). This stage describes the cancer that involves only the ducts and lobules of the breast tissue. It does not involve the surrounding tissue of the breast.
Stage 1 breast cancer
Stage one breast cancer describes invasive breast cancer. Invasive cancer is the one in which cancerous cells break through to or invade normal surrounding breast tissue. Stage 1 is divided into two subcategories known as IA and IB.
Stage 1A breast cancer
Stage IA describes invasive breast cancer if any of the following conditions exists:
- the tumor measures up to 2 centimeters
- cancer has not spread outside the breast
- no lymph nodes are involved
Stage 1B breast cancer
Stage IB describes invasive breast cancer with any of the following conditions:
- there is no tumor in the breast but cancerous cells are found in the lymph nodes which are larger than 0.2 millimeters but not larger than 2 millimeters.
- there is a tumor in the breast not larger than 2 centimeters, and there are small groups of cancer cells in the lymph nodes which are larger than 0.2 millimeters but not larger than 2 millimeters.
Stage 2 breast cancer
Stage two breast cancer signifies that the cancer is either in the breast or in the nearby lymph nodes or both. It is an early stage breast cancer. Stage 2 is subdivided into 2A and 2B.
Stage 2A breast cancer
Stage 2A describes the invasive breast cancer with any of the following conditions:
- there is no tumor in the breast, but cancer (larger than 2 millimeters) is found in 1 to 3 axillary lymph nodes under the arm or in the lymph nodes near the breastbone
- the tumor (2 centimeters or smaller) has spread to the axillary lymph nodes
- the tumor (2 to 5 centimeters large) has not spread to the axillary lymph nodes
Exceptions
A cancer tumor is likely to be classified as stage 1B if:
- it measures between 2 and 5 centimeters
- it has not spread to the lymph nodes or parts of the body away from the breast
- there is HER2-negative
- there is hormone-receptor-positive
A cancer tumor is likely to be classified as stage 1A if:
- it measures between 2 and 5 centimeters
- it has not spread to the lymph nodes
- its HER2 status is negative
- its estrogen-receptor status is positive
- its progesterone-receptor status is negative
- it has an Oncotype DX Recurrence Score of 9
Stage 2B breast cancer
Stage 2B describes invasive breast cancer in which:
- the tumor (2 to 5 centimeters large) is present and cancer in small groups of breast cancer cells (0.2 to 2 millimeters large) are found in the lymph nodes
- the tumor (2 to 5 centimeters large) has spread to 1 to 3 axillary lymph nodes or to lymph nodes near the breastbone
- the tumor (larger than 5 centimeters) has not spread to the axillary lymph nodes
Exceptions
A cancer tumor is likely to be classified as stage 1B if it:
- measures between 2 and 5 centimeters and:
- cancer is found in 1 to 3 axillary lymph nodes
- its HER2 status is positive
- its estrogen-receptor status is positive
- its progesterone-receptor status is positive
Stage 3 breast cancer
Stage three breast cancers refer to cancers that have spread from the breast to lymph nodes close to the breast or to the skin of the breast or to the chest wall. It is also called locally advanced breast cancer. Stage 3 breast cancer is further divided into 3A, 3B, and 3C.
Stage 3A
Stage 3A describes invasive breast cancer with any of the following conditions:
- there is no tumor in the breast or the tumor may be of any size and cancer is found in 4 to 9 axillary lymph nodes or in the lymph nodes near the breastbone
- the tumor is larger than 5 centimeters; small groups of breast cancer cells (0.2 to 2 millimeters large) are found in the lymph nodes
- the tumor is larger than 5 centimeters; cancer has spread to 1 to 3 axillary lymph nodes or to the lymph nodes near the breastbone
Exceptions
A cancer tumor is likely to be classified as stage 1B if:
- it measures more than 5 centimeters across
- it is of grade 2
- the cancer is found in 4 to 9 axillary lymph nodes
- its estrogen-receptor status is positive
- its progesterone-receptor status is positive
- its HER2 status is positive
Stage 3B
Stage 3B describes invasive breast cancer with any of the following conditions:
- the tumor may be any size and has already spread to the chest wall and/or the breast skin, which would have caused swelling or an ulcer, and
- the tumor may have spread to up to 9 axillary lymph nodes or may have spread to lymph nodes near the breastbone
Inflammatory breast cancer is considered at least stage IIIB. Typical features of inflammatory breast cancer include:
- redness over a significant portion of the breast skin
- the breast feels warm and may be swollen
- cancer cells have spread to the lymph nodes and may be found in the skin
Exceptions
A cancer tumor is likely to be classified as stage 2A if:
- it measures more than 5 centimeters across
- it is grade 3
- the cancer is found in 4 to 9 axillary lymph nodes
- its estrogen-receptor is positive
- its progesterone-receptor is positive
- its HER2 status is positive
Stage 3C
Stage 3C describes invasive breast cancer with any of the following conditions:
- there is no sign of cancer in the breast or, if there is a tumor, it may be any size and may have spread to the chest wall and/or the skin of the breast, and
- the cancer has spread to 10 or more axillary lymph nodes or the cancer has spread to lymph nodes above or below the collarbone or the cancer has spread to axillary lymph nodes or to lymph nodes near the breastbone.
Exceptions
A cancer tumor is likely to be classified as stage 3A if:
- it measures any size
- it is grade 2
- its estrogen-receptor status is positive
- its progesterone-receptor status is positive
- its HER2 status positive or negative
Stage 4 breast cancer
Stage four breast cancer describes invasive breast cancer that has:
- spread away from the breast and nearby lymph nodes to other far away organs of the body, such as the lungs, skin, bones, liver, or brain, or distant lymph nodes.
Stage 4breast cancer is also known as advanced cancer or metastatic cancer. Cancer can be diagnosed as stage IV and is known as “de novo” by doctors. A recurrence of a previous breast cancer that has spread to other parts of the body can also be stage 4 breast cancers.
