Lymph Node Status and Breast Cancer

How Lymph Nodes Are Used in Diagnosis

Front view of female breast anatomy with a lump present

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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.

A sentinel node biopsy is a procedure in which lymph nodes are surgically removed so that the cells can be examined under a microscope.

Lymph Node Status

If your lymph nodes are clear of cancer, they are considered negative or clear and given a rating of N0. Lymph nodes that contain a tiny amount of cancer cells (referred to as micrometastasis) 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: 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.

Generally speaking, women with N0, N1, and N2 lymph node status have no significant difference in survival times given the effectiveness of newer therapies. The overall survival of women with N3 status is significantly lower, although the survival times can vary dramatically based on the degree of metastasis and other factors.

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 score will be used along with other test results—including the type of cancer cell type involved (such as adenocarcinoma, squamous cell carcinoma, etc.)—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).

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