The stage of a breast cancer describes the extent of the cancer in your breast and in the body.

When doctors stage the breast cancer, they look at these factors:

• how far the cancer has spread, using a system called TNM (tumor, lymph nodes, metastasis)
  • the size of the tumor (T)
  • whether lymph nodes near the breast contain breast cancer (N)
  • whether the breast cancer has spread from the breast to other parts of the body (M)
• characteristics of the cancer cells that show how the cancer is behaving
  
  • estrogen receptor (ER) status: whether the cancer has proteins to which the hormone estrogen attaches
  • progesterone receptor (PR) status: whether the cancer has proteins that attach to the hormone progesterone
  • HER2 status: whether the cancer is making too much of a protein known as HER2
  • grade (G): how similar the cancer cells look to normal cells

In some cases, Oncotype Dx score, which measures the risk of recurrence, is part of staging.

Breast cancer stages can be clinical or pathological. The clinical stage is based on a physical exam by your doctor and any scans, including mammogram, ultrasound, and MRI, that you have had. Pathologic stage is based on what is found during surgery to remove the cancer. Pathologic stage is more precise, but clinical stage may be use to guide treatments given before surgery.

Stage is one piece of information doctors use to understand how well a treatment might work. Stage, along with other factors including advances in treatment, is also used to estimate survival rates.

Stage 0

Stage 0 breast cancer is noninvasive. This means the cancer cells are contained inside of the ducts of the breast and no cancer cells can be seen breaking through to surrounding breast tissue. Ductal carcinoma in situ, or DCIS, is stage 0 breast cancer.

Stage I

Stage I breast cancers are invasive. This means that the cancer has broken through the ducts or lobules into surrounding breast tissue. Stage I breast cancers are 2 centimeters or smaller in size. Usually, these cancers have not traveled to the lymph nodes.

Stage I breast cancer falls into two groups: stages IA and IB.

• Stage IA breast cancers usually have the following characteristics:
  • The tumor is 2 centimeters (about the size of a peanut without the shell) or smaller. This can include very small tumors of less than 1 millimeter (microinvasive breast cancer).
  • There is no cancer in the lymph nodes.
  • The cancer has not spread beyond the breast to any other organs. 
     
• Stage IB breast cancers include these situations:
  • There is no evidence of a breast tumor, but there are small areas of cancer in the underarm (axillary) lymph nodes measuring at least 0.2 millimeters but are no larger than 2 millimeters in size, called micrometastasis.
  • There is a breast tumor that is 2 centimeters or less across, including as small as 1 millimeter or less (microinvasive breast cancer), and there are small areas of cancer in the axillary lymph nodes (micrometastasis) measuring at least 0.2 millimeters but are no larger than 2 millimeters in size. 
  • In all cases of stage IB breast cancer, the cancer has not spread to any other organs

Hormone receptor status, HER2 status, and cancer grade are also factors in determining whether a cancer is stage I.

Stage II

Stage II breast cancers fall into two groups: IIA and IIB.

• Stage IIA includes these situations:
  • There isn’t any evidence of a breast tumor, but there is cancer in one to three axillary lymph nodes or internal mammary lymph nodes (near the breast bone, identified with sentinel lymph node biopsy). 
  • The tumor is 2 centimeters or less across and there is cancer in one to three axillary lymph nodes and/or internal mammary lymph nodes. 
  • The tumor is between 2 and 5 centimeters across and there is no cancer in the lymph nodes.
  • In all cases, cancer has not spread beyond the breast to any other organs. 
     
• Stage IIB includes these situations:
  • The tumor is between 2 and 5 centimeters across and there is cancer in one to three axillary lymph nodes or internal mammary lymph nodes (near the breast bone, sometimes identified with sentinel node biopsy).
  • The tumor is more than 5 centimeters across and there is no cancer in the lymph nodes, or a tiny amount of cancer has been detected in lymph nodes at a size smaller than 0.2 millimeters.
  • In all cases, cancer has not spread beyond the breast to any other organs.

Hormone receptor status, HER2 status, and cancer grade are also factors in determining whether a cancer is stage II.

Stage III

Stage III breast cancers fall into three groups: stages IIIA, IIIB, and IIIC.

• Stage IIIA includes these situations:
  • There is no evidence of a tumor, or there is a tumor of any size and cancer is found in four to nine axillary lymph nodes, or the cancer has caused the internal mammary lymph nodes near the breast bone to become enlarged.
  • The tumor is larger than 5 centimeters across and there is cancer in one to three axillary lymph nodes or internal mammary lymph nodes near the breast bone, found during a sentinel node biopsy.
  • In all cases, the cancer has not spread to distant organs such as the bones, lungs, or liver.
     
• Stage IIIB includes these situations:
  • The tumor may be of any size that has grown into the skin or the chest wall.
  • Cancer may be found in 0 to 9 axillary lymph nodes.
  • Cancer may have one or more enlarged internal mammary lymph nodes near the breast bone.
  • The breast cancer may also be inflammatory. Inflammatory breast cancer is breast cancer that has certain physical signs that appear and worsen quickly, these can include breast redness, warmth, swelling, or an “orange peel” look on the breast skin. Inflammatory breast cancer usually does not form a lump and may not be found in a mammogram. Inflammatory breast cancers can be hormone receptor positive, HER2 positive, or triple negative.
  • In all cases, the cancer has not spread to distant organs such as bones, lungs, or liver.
     
• Stage IIIC breast cancers may have a tumor of any size or no tumor at all, when cancer is found
  • in 10 or more axillary lymph nodes in any number of internal mammary lymph nodes near the breast bone
  • in a combination of axillary and internal mammary lymph nodes
  • in supraclavicular lymph nodes (lymph nodes near the collarbone)
  • to be inflammatory breast cancer. This means it has certain physical signs that appear and worsen quickly, these can include breast redness, warmth, swelling, or an “orange peel” look on the breast skin. Inflammatory breast cancer usually does not form a lump and may not be found in a mammogram. Inflammatory breast cancers will also be either hormone receptor-positive, HER2-positive, or triple negative.
  • to have not spread to distant organs such as bones, lungs, or liver.

Hormone receptor status, HER2 status, and cancer grade are also factors in determining whether a cancer is stage III.

Stage IV

Stage IV or metastatic breast cancer is invasive cancer that has spread beyond the breast to other parts of the body. Common locations of spread can include

• Lymph nodes in distant parts of the body
• The chest wall
• The bones, liver, lungs, or brain

Stage IV breast cancer is often a recurrence, or the return of a previous breast cancer. If stage IV is the very first diagnosis of breast cancer, it’s often called de novo (“starting from the beginning”) metastatic breast cancer.

Advanced breast cancer vs. metastatic breast cancer

You might hear stage IV breast cancer referred to as advanced or metastatic. It’s important to know that “advanced” can mean stage IV breast cancer, but it can also refer to “locally advanced” breast cancer. Locally advanced breast cancer has spread to areas near the breast, including lymph nodes, skin, and/or the chest wall, but not to other locations of the body. Inflammatory breast cancer can be locally advanced or metastatic.

The TNM system

After you receive a breast cancer diagnosis, your doctor may ask for radiology tests, more biopsies, a physical exam and more details from you about your symptoms. With all this information, your doctor will assign a stage to the breast cancer using the American Joint Committee on Cancer TNM system.

The TNM system is the most widely used systems to describe the stages of breast cancer. Most cancer care teams use the TNM system as a standard way to describe how far the cancer has spread. Doctors use the TNM stage of the cancer to make decisions about which treatments are best for you.

Each letter in the TNM system is assigned a number to show the size of the original tumor and how far the cancer has spread. Here, we’ll walk you through what it all means.