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The Role of Lymph Nodes in Breast Cancer

One of the first places breast cancer can spread and grow is in nearby lymph nodes, which are part of the body’s lymphatic (lymph) system. The immune system relies on the lymphatic system, which is made up of three parts:

  1. Lymph, a clear fluid that circulates through the lymphatic system
  2. Lymphatic vessels
  3. Lymph nodes

The main function of the lymph system is to circulate lymph, which contains white blood cells that fight infections, throughout the body and to flush your body of toxins, waste, and other unwanted materials.

Breast cancer cells that continue to multiply can enter the lymphatic vessels that are located in breast tissue. The lymph fluid then carries the cells throughout the body. In many cases, the lymph nodes found in the underarm area are the first place breast cancer will spread to since they are the closest to the breast.

The tests used by your cancer specialist to determine that there are breast cancer cells in the lymph nodes is called lymph node involvement.

Determining Lymph Node Involvement

To determine if lymph nodes are involved, your breast cancer specialist will remove one or several underarm lymph nodes so they can be biopsied and then examined under a microscope.

Lymph nodes can be checked in two different ways. The most common and least-invasive method is called sentinel lymph node biopsy. The other is called axillary lymph node dissection.

Lymph node surgery is typically done as part of the primary surgery to remove the breast cancer. There are situations where it may be done as a different operation.

Sentinel Lymph Node Biopsy (SLNB)

A sentinel lymph node is the first lymph node to which cancer cells are most likely to spread to from a primary tumor. There are instances where more than one sentinel lymph node is present.

The sentinel node is identified and taken out during surgery to remove early-stage breast cancer. It will then be sent to a pathologist— a physician who studies the causes and effects of diseases. The pathologist will determine if there is cancer in the removed sentinel node. This procedure is called a sentinel lymph node biopsy (SLNB).

In order to identify the sentinel node the surgeon will:

  • Inject a radioactive substance, a blue dye, or both near the tumor
  • Use a device that detects radioactivity to find the sentinel node or looks for lymph nodes that are stained with the blue dye
  • Make a small incision (about 1/2 inch) in the overlying skin and remove the node once it has been located

The results of the pathology exam help determine breast cancer stage and help plan treatment.

If the sentinel nodes show no sign of cancer (lymph node-negative), surgery to remove more lymph nodes will not be needed because it is unlikely other lymph nodes have cancer. However, if cancer is present in the sentinel nodes (lymph node-positive), more lymph nodes may be taken out with a procedure called axillary dissection.

Sentinel Lymph Node Biopsy

Axillary Lymph Node Dissection (ALND)

Axillary lymph nodes run from your breast tissue into the armpit. This area under the arm is called the axilla.

During an axillary lymph node dissection, there can be anywhere from 10 to 40 lymph nodes removed and examined. Typically, these nodes are removed during your lumpectomy or mastectomy.

Lymph Node Status and Breast Cancer Treatment

The pathology report (the biopsy results) will show how many lymph nodes were removed and how many were “involved” (tested positive for cancer). This is referred to as lymph node status.

If the pathology report shows a node-negative status, this means the breast cancer has not spread to nearby lymph nodes. A node-positive status, on the other hand, means that cancer is present in the lymph nodes. Positive results also mean that the cancer may have already or could possibly spread to other organs, such as the bones, liver, lungs, and brain. In order to determine that, your AO cancer care team would need to conduct further tests.

The pathology report will also show how much cancer is in each node. Cancer cells can range from small in size and few in number to large in size and many in number. This information may be reported as:

  • Microscopic (or minimal): This means only a few cancer cells are in the node and that a microscope is needed to find them.
  • Gross (also called significant or macroscopic): This means there is a lot of cancer in the node and that it can be seen or felt without the use of a microscope.
  • Extracapsular extension: This means the cancer has spread (metastasized) outside the wall of the node.

Lymph node status can affect breast cancer treatment decisions as well as the prognosis (outlook). If there is cancer found in the lymph nodes, it is likely that your oncologist will recommend chemotherapy in addition to surgery, since chemotherapy can attack cancer cells throughout the lymph system.

Early detection is key. Because of this, we encourage you to perform self-exams and have regular mammograms as both can be helpful in finding breast cancer early. The earlier breast cancer is detected, the less chance of it spreading to the lymph nodes.