Lymph Node Status and Breast Cancer

The number and location of your affected lymph nodes are an important part of the diagnosis of breast cancer. The information is used—along with characteristics of the primary tumor and the degree of cancer metastasis (spread)—to determine the stage of the malignancy and your prognosis (long-term outlook) after cancer treatment is completed.

Role of Lymph Nodes

Lymph nodes are clustered in different parts in the body and serve as filters to help trap and neutralize disease-causing microorganisms. Those nearest the breast, called axillary lymph nodes, are located just under the armpit.

Because cancer cells shed from the primary tumor come into contact with the axillary lymph nodes first, these will be the lymph nodes doctors will look at first to determine whether cancer has spread.

When breast cancer spreads to axillary lymph nodes, it does so in an orderly fashion, since the nodes are naturally displayed in the form of a chain or stations. Finding the first lymph node in the chain is a useful way to detect if the cancer has made its way into the axillary lymph nodes. This is done by a procedure called sentinel node biopsy. If the first lymph node of the chain (the sentinel) has no cancer in it, it is an indication that cancer has not made it to the axilla and therefore unneeded surgical procedures in this area can be avoided. 

Lymph Node Status

If your lymph nodes are clear of cancer, they are considered negative or clear and given a rating of N0 (N-Zero). Lymph nodes that contain cancer cells are considered positive, and rated N1, N2, or N3, depending on the number of lymph nodes affected as well as their location.

The rating of lymph nodes can be broadly described as follows:

• N0 (N-Zero): No cancer cells have been found.
• N1: Cancer is found in 1 to 3 lymph nodes either under the arm or within breast tissue.
• N2: Cancer is found in 4 to 9 lymph nodes either under the arm or within breast tissue.
• N3: Cancer is found in 10 or more lymph nodes under the arm, within breast tissue, or above or below the collarbone.

If cancer has spread to lymph nodes, it is considered to be "locally advanced" (in contrast to distant advancement or metastases) and this has prognostic value; it generally confers a worse prognosis. The nature of the cells that make up the cancer (including but not limited to: the presence of hormone receptors on the surface of the cells), the patient's characteristics, and other factors help complete the picture of prognosis of a particular cancer. Despite a cancer being locally advanced, many times it remains a highly treatable and oftentimes curable cancer.

Even with advanced metastatic disease, one in four women will live for five years or more.

Staging Breast Cancer

The lymph node rating plays an important role in the staging of cancer. The staging is performed so that the appropriate treatment can be delivered, ensuring that you are neither overtreated nor undertreated. It also helps determine your prognosis, including a rough estimate of your life expectancy following treatment.

The staging system most widely used for breast cancer is called the TNM system. TNM combines the results of three primary factors:

• Tumor size (T)
• Lymph node status (N)
• Metastasis (M), whether it is present or not

Your TNM will be used along with other test results—including the type of cancer cell type —to establish the treatment plan.

In 2017, the American Joint Committee on Cancer announced changes to the cancer staging system. Today, in addition to tumor size, lymph node status, and presence of metastasis, the staging of breast cancer also includes the determination of the tumor's hormone status (whether it is influenced by estrogen or progesterone) and the HER2 status (higher than normal levels of proteins on breast cancer cells, which make them more receptive to certain drugs).