Breast cancer staging

The stage of breast cancer, along with its type, determines treatment options. Here's a summary of factors considered in breast cancer staging.

After discovering that you have breast cancer, your doctor will decide what additional tests may be helpful to find out if the disease has spread outside the breast. Called staging, this process provides information on the extent of the disease. The cancer stage — noted as a number from 0 to IV — is based on the size of the tumor and whether the cancer has spread to the lymph nodes. Breast cancer staging helps you and your doctor plan your treatment and understand the most likely outcome (prognosis).

To determine your cancer stage, your doctor will ask questions about your medical history, do a careful physical examination and review all the tests you've had as well as the results from the biopsy of the tumor or suspicious area. Additional tests, such as X-rays and blood work, may be needed. In general, the stage isn't fully known until after the operation to remove the tumor in your breast and sample the lymph nodes under your arm.

Breast cancer staging is complicated, and the classification system sometimes changes as doctors learn more about breast cancer. All the numbers and letters can be confusing, but these details help you and your doctor know as much as possible about your cancer.

Breast cancer staging tests

Most women with a new diagnosis of breast cancer don't need all the diagnostic tests available. Usually the information from the surgical pathology report, physical exam, medical history, blood tests and a chest X-ray is enough.

Blood tests. These may include a complete blood count (CBC), which gives a picture of your general health, and a blood chemistry test to assess your kidney and liver function. If other evidence suggests that your cancer has spread to distant parts of your body, you may have your blood tested for abnormal levels of substances known as tumor markers. Unfortunately, the available tumor markers aren't reliable for breast cancer — they don't show the presence or absence of breast cancer. As a result, the tumor markers are used only in very specific circumstances, rather than for most women with breast cancer.
Chest X-ray. This may be done to find out if the cancer has spread to your lungs.
Additional tests. These may include a bone scan to check for spread of cancer to your bones, and other imaging tests — computerized tomography (CT), MRI or positron emission tomography (PET) — to see if the cancer has spread to other organs. Not all women or men with breast cancer should have these tests done. Your doctor can help you determine if these tests are necessary.

Staging classification

The most common staging method, called the TNM staging system, includes three key components:

Tumor (T). How big is the tumor, and has it spread to the skin or chest wall muscle? Tumor size is one of the most important predictors of how a cancer will behave.
Node (N). Have cancer cells spread to nearby lymph nodes? Doctors count how many lymph nodes under the arm (axillary lymph nodes) test positive for cancer, because their status strongly relates to prognosis. Breast cancers may be described as "node positive" or "node negative."
Metastasis (M). Has the cancer spread to other, distant areas of the body?

The number assignments in these categories indicate the degree of tumor growth or spread. For example, N0 means no axillary lymph nodes are affected, while N1 means 1 to 3 nodes are positive and N2 means 4 to 9 positive nodes.

Breast cancer stages

Once the surgery is completed, your doctor can determine the stage of your cancer. Breast cancer stages range from 0 to IV, with many subcategories. Lower numbers indicate earlier stages of cancer, while higher numbers reflect a late-stage cancer.

Stage 0
This stage describes noninvasive (in situ) breast cancer. It hasn't spread within the breast or to other parts of the body. Ductal carcinoma in situ (DCIS) is an example of stage 0 cancer.

Stage I
This stage is an early stage of invasive breast cancer in which:

The tumor measures no more than 2 centimeters (cm) in diameter (3/4 inch)
No lymph nodes are involved — the cancer hasn't spread outside the breast

Stage II
This stage, subdivided into IIA and IIB, describes invasive breast cancers in which one of the following is true:

The tumor measures less than 2 cm but has spread to lymph nodes under the arm
No tumor is found in the breast but cancer is found in the axillary lymph nodes
The tumor is between 2 cm and 5 cm (about 1 to 2 inches) and may have spread to lymph nodes under the arm
The tumor is larger than 5 cm but hasn't spread to any lymph nodes

Stage III
Stage III breast cancers are subdivided into three categories — IIIA, IIIB and IIIC — based on a number of different criteria. By definition, stage III cancers haven't spread (metastasized) to distant sites.

For example, a stage IIIA tumor is larger than 5 cm and has spread to one to three lymph nodes under the arm. Other stage IIIA tumors may be any size and have spread into multiple lymph nodes. The lymph nodes clump together and attach to one another or to the surrounding tissue.

In stage IIIB breast cancer, a tumor of any size has spread to tissues near the breast — the skin and chest muscles — and may have spread to lymph nodes within the breast or under the arm. Stage IIIB also includes inflammatory breast cancer, an uncommon but aggressive type of breast cancer.

Stage IIIC cancer is a tumor of any size that has spread:

To 10 or more lymph nodes under the arm
To lymph nodes above or beneath the collarbone and near the neck
To lymph nodes within the breast itself and to lymph nodes under the arm

Stage IV
Stage IV breast cancer has spread to other, distant parts of the body, such as the lungs, liver, bones or brain.

Estimating your outlook

Identifying the stage of your cancer helps your doctor decide on an appropriate treatment strategy. The stage also helps predict how well you might do — whether the cancer will come back (recurrence), for instance. Based on statistics collected from other women's experiences, scientists can estimate the five-year disease-free survival rate — the percentage of women who remain free of disease five years after their cancers were diagnosed.

Another way to express the outlook for your disease is the five-year overall survival rate — the percentage of women who are still alive five years after the breast cancer diagnosis. Five-year survival is lower among women with a more advanced stage of cancer at diagnosis. In general, the larger the tumor and the more lymph nodes involved, the more likely the cancer is to recur or spread to other parts of the body. Among all people with breast cancer, five-year survival is 98 percent for early-stage, localized cancer, 84 percent for regional cancer, and 27 percent for stage IV, distant-spread cancer.

The breast cancer stage isn't the only factor doctors consider when deciding on treatment. Other key information includes:

The tumor grade and size
The presence or absence of receptors for the hormones estrogen and progesterone
The amount of a protein called HER-2 produced by the cancer cells
Your menopausal status
Your general health

Newer methods of estimating survival and the possibility of recurrence look at many of these variables. This detailed information about specific tumors paves the way for more individualized breast cancer treatment. Doctors can use online calculators that take into account all the variables above and estimate the added benefits of chemotherapy, hormonal therapy or no treatment.

A new test (Oncotype DX) done directly on cancer cells can also help determine if added treatments will help you. This test is used only for women with small, estrogen receptor positive, node-negative breast cancers. It can help you and your doctor know if you need chemotherapy or can safely avoid it.

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