A sentinel lymph node biopsy (SLNB) is a type of surgery. It’s used to help diagnose and treat breast cancer. It can help your doctor determine the stage of your breast cancer, including whether or not it has spread outside of your breast. The knowledge your doctor gains from this procedure will guide your treatment plan.

To perform a SLNB, your doctor will inject a radioactive tracer or blue dye into your breast. Your body will naturally drain the tracer or dye into the sentinel lymph node. The sentinel node is the node that breast cancer is most likely to travel to first once it leaves the breast. Once your doctor has identified the sentinel node, they will surgically remove it. Then a pathologist will examine it for cancer cells. If they don’t find any cancer cells in the sentinel node, the surgeon will not remove any additional nodes. If they do find cancer cells, you may need to undergo an axillary dissection where additional lymph nodes are surgically removed. In some cases, your doctor will identify and remove more than one sentinel lymph node.

The treatment for breast cancer varies, depending on its stage. Your doctor will stage your cancer based on:

  • the size of the tumor in your breast
  • how many lymph nodes, if any, are found to have cancer cells in them
  • if the cancer has spread or metastasized to other distant organs

If your cancer remains in your breast, there’s a good chance it can be cured. It can potentially spread to vital organs, such as your brain, liver, or lungs. This process is called metastasis. If it spreads to other parts of your body, the chance of treatment being able to cure it decreases.

Your doctor must learn how far your cancer has spread in order to treat you properly. When cancer cells are “on the move,” they typically travel through your lymphatic system. Your lymph nodes are an important part of this system. A SLNB can help your doctor determine if your breast cancer has reached your lymph nodes.

In some cases, your doctor may perform a SLNB as an outpatient procedure. In other cases, you may need to stay overnight in the hospital. Your doctor may perform it at the same time as your breast cancer surgery and breast reconstruction.

After the sentinel lymph node or nodes are identified, you will go to the operating room.

While you’re under anesthesia, your doctor will make an incision in your armpit to remove the sentinel lymph node. In some cases, they may remove one or two other lymph nodes as well. A pathologist will examine them for cancer cells. They will likely do this while you’re still under anesthesia.

If the pathologist finds cancer cells, your doctor may remove additional lymph nodes. This is called an axillary dissection. In an axillary node dissection, they remove many axillary nodes and test them for cancer. Not all of these nodes will necessarily be cancerous. For example, they may remove 12 nodes and find that five have cancer cells in them.

A SLNB will help your doctor determine the stage of your cancer. If your biopsied lymph nodes are negative for cancer calls, your breast cancer probably hasn’t spread outside of the breast. Your follow-up steps will depend on the stage and subtype of your breast cancer. You may or may not need chemotherapy, radiation therapy, or other treatments.

If your biopsied lymph nodes are positive for cancer cells, your doctor will likely remove additional lymph nodes. You may need further imaging tests to look for cancer in other areas of your body. These tests can include a CT scan, MRI, or bone scan. Your treatment will depend on the subtype of your cancer and may include chemotherapy, radiation, or hormone therapy.

Your doctor can help you understand the results of your biopsy and appropriate follow-up steps.

A SLNB can help your doctor stage your breast cancer without removing unnecessary lymph nodes. The more nodes that are removed, the more likely that you will have side effects from the surgery like decreased mobility, lymphedema, numbness, or pain. In an axillary node dissection, several nodes are removed and then reviewed by the pathologist after the surgery. It is not usually known at the time of the surgery if the lymph nodes are cancerous.

Like other forms of surgery, a SLNB poses some risks. For example, you may develop pain, swelling, bruising, or infection at the surgical site. You may also experience nerve injury. Lymphedema may also occur, especially if your doctor removes more than one lymph node. Lymphedema happens when the lymph nodes are damaged or absent and no longer able to promote proper lymphatic drainage. This can result in arm swelling and decreased range of motion. It can be permanent in some cases.

It’s also possible to receive a false-negative biopsy result on a SLNB. Errors happen when your pathologist or surgeon makes a mistake or if the dye injection was not done correctly. It’s also possible that cancer cells pass through a sentinel node and lodge in another lymph node. False negatives can give you a false sense of security, leading you to believe that your cancer hasn’t spread when it actually has.

For most people, the potential benefits of a SLNB outweigh the risks. Your doctor can help you weigh the benefits and risks.

When you have breast cancer, an early and accurate diagnosis can improve your outlook. It will also help guide your treatment plan. A SLNB can help your doctor determine if your cancer has spread to your lymph nodes. They can help you understand the potential benefits and risks of this procedure.