The lymphatic system is one of the body's primary tools for fighting infection. This system contains lymph fluid and lymph nodes, which occur in critical areas in the body. Cancer cells sometimes enter and build up in the lymph system.

Lymph nodes are responsible for filtering lymph fluid and detecting chemical changes that signal an infection is present. When these filter points are in the armpit, doctors call them axillary lymph nodes.

As axillary lymph nodes are near the breasts, they are often the first location to which breast cancer spreads if it moves beyond the breast tissue.

The number of axillary lymph nodes can vary from person to person, ranging from five nodes to more than 30.

After a breast cancer diagnosis, a doctor will often check whether cancer cells have spread to the axillary lymph nodes. This can help confirm the diagnosis and staging of the cancer.

In this article, we explain the link between breast cancer and the axillary lymph nodes.

Breast cancer may spread to the axillary lymph nodes in the armpits.Share on Pinterest
Breast cancer may spread to the axillary lymph nodes in the armpits.

Breast cancer usually spreads to the axillary lymph nodes before those at any other location. Given their close proximity to the breasts, these lymph nodes are a common place where breast cancer spreads.

As a general rule, when cancer spreads from its starting point, it becomes harder to treat. The outlook also worsens.

Breast cancer treatment often requires a mastectomy, which is the removal of one or both breasts. An alternative is a lumpectomy, which is the removal of the tumor and surrounding tissue.

If cancer has spread to the axillary lymph nodes, a doctor may recommend extracting the lymph nodes during this procedure to remove the cancerous cells.

Lymph nodes are responsible for draining lymph fluid. As a result, their removal can cause some side effects after surgery. One side effect can be lymphedema of the arm, which causes a type of chronic swelling.

Axillary lymph nodes often feel like small, round sponge like masses under the skin. They may be painful to the touch. A doctor will investigate if cancer has spread to the lymph nodes by performing a physical examination or an ultrasound.

The doctor will feel around the collarbone, neck, and underarms for signs of swollen lymph nodes.

According to some estimates, testing reveals cancerous lymph nodes in one-third of women who do not show signs of swollen lymph nodes during physical examination. As a result, it is essential to conduct further testing in most people.

A doctor has several different diagnostic methods to determine whether cancer has spread to the axillary lymph nodes.

Sentinel node biopsy

A sentinel node biopsy involves injecting a radioactive substance or dye into the breast. The dye will move to certain lymph nodes before others.

A doctor will use imaging to identify the sentinel lymph nodes, which are the initial lymph nodes that the dye reaches.

A doctor removes one or more sentinel nodes and sends the sample to a pathologist who specializes in identifying types of cancerous cell. This approach can help a person avoid the side effects of removing multiple axillary lymph nodes.

Axillary dissection

Axillary dissection is a procedure that involves removing more lymph nodes under the armpit.

The doctor removes an area of fat that contains many or all of the lymph nodes. Using this sample, they will then request testing to determine whether cancer has spread beyond the sentinel lymph nodes and the extent of the spread.

During treatment, the cancer specialist, or oncologist, targets the lymph nodes with radiation, as well as the breast. The radiation helps remove any remaining cancer cells.

Staging

breast cancer consultationShare on Pinterest
By identifying how far breast cancer has spread, a doctor can assign a stage to it.

The stage of cancer indicates the extent and spread of the disease. Knowing the stage can inform the outlook and treatment plan.

Doctors use the TNM system to work out the stage of breast cancer. TNM stands for tumor, nodes, and metastasis:

  • The tumor staging defines the size of the original tumor.
  • The metastasis staging gives information on whether cancer has spread to other parts of the body from its site of origin.
  • The node staging tells whether breast cancer has reached the lymph nodes, and how many nodes show signs of cancer cells.

The node staging has several subcategories to provide more specific detail:

NX: Assessment of the axillary lymph nodes is not possible if, for example, a person has already undergone surgery to remove them.

N0: Cancer has not spread to the lymph nodes. However, a doctor may request further testing to see if microscopic amounts of cancer cells are present in the lymph nodes. These cells are known as micrometastases.

N1: Micrometastases or cancerous cells are present in 1–3 axillary lymph nodes, or the nodes inside the breast, and show very small amounts of cancerous cells.

N2: In this stage, 4–9 axillary lymph nodes have cancerous cells. A doctor also uses this stage to indicate that the nodes inside the breast have developed cancer. These nodes are known as internal mammary nodes.

N3: This stage takes into account a broad spectrum of outcomes, as follows:

Testing found cancer in 10 or more axillary lymph nodes.

  • Cancer is in the lymph nodes under the clavicle, or collarbone.
  • Cancer is in the internal mammary nodes and one or more axillary lymph nodes.
  • Four or more axillary lymph nodes are cancerous, and internal mammary nodes have micrometastases.
  • Testing discovered cancerous nodes above the clavicle.

The staging of axillary lymph nodes becomes higher when cancer has spread to more nodes and different types of node. Treatment becomes more difficult, and the outlook is less positive, as the staging number increases.

Here, learn how fast breast cancer can spread in one year.

If breast cancer spreads to the axillary lymph nodes, the outlook becomes worse.

However, lymph node staging is only one consideration when a doctor gives a cancer prognosis.

A doctor will also consider the overall size of a tumor, the type of cells present, and whether cancer has spread to other organs.

Other factors can further affect the outlook, including a person's overall health and medical history.

Q:

Does breast cancer spread to lymph nodes outside of the armpits?

A:

Breast cancer can spread to any lymph nodes. Most often, it spreads to the axillary lymph nodes first (in the armpit), and then to the nodes in the collarbone (clavicular) or the breast (internal mammary).

Yamini Ranchod, PhD, MS Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.