Identifying the sentinel lymph node is an important step in making a treatment plan for many types of cancer.

The sentinel lymph node is the lymph node that cancer usually spreads to first if it’s going to metastasize to other areas of your body. Examining this lymph node will help your doctor determine the stage of your cancer and how to treat it.

This article will explain more about the sentinel lymph node, how your doctor will determine which lymph node that is, and how the information in that lymph node can help guide your cancer treatment.

Lymph nodes are small organs spread throughout the body as a part of the lymphatic system. This system works with the immune system to help filter fluids and remove things like waste, bacteria, and viruses from your body.

Think of the lymphatic system as a highway that waste and fluids travel through before exiting your body.

Also on this highway are white blood cells acting as the highway patrol to remove any unwanted visitors like bacteria, viruses, or cancer cells. Lymph nodes are the rest stops where bits of debris and immune cells gather.

For people who have certain types of cancer, lymph nodes may contain bits of tumors or cancer cells that have separated from the primary location, traveling along the highway before settling at a pit stop.

If the white blood cells (highway patrol) don’t stop these cancer cells, they can move along the lymphatic highway to other parts of the body.

The sentinel lymph node is the lymph node where cancer is most likely to spread to first if it’s going to metastasize from a primary cancer site to other areas of the body.

In other words, it’s the first exit cancer cells take after they get on the lymphatic highway.

Finding cancer cells in a lymph node is usually a sign that your cancer is spreading, or metastasizing, to other parts of your body.

Sentinel node mapping is used to predict which lymph node is the most downstream from your primary cancer site. It’s usually used to help stage breast cancers and melanoma.

A sentinel node biopsy can then help confirm or rule out the spread of cancer, but the first step is determining which lymph node is best to biopsy.

Mapping is done before a biopsy using a mildly radioactive liquid that’s injected into the site of your primary cancer or tumor.

Once the liquid has been injected, the area is massaged and a technician will use some type of imaging device to tract where the radioactive fluid is headed.

This will tell them the direction of the lymph flow from the primary cancer site and, ideally, lead them to the sentinel lymph node.

Once the sentinel lymph node has been identified, a biopsy will be performed to take a sample of tissue for additional testing.

This testing should be able to reveal whether cancer cells have made it to this lymph node. This is done immediately after or at the same time as sentinel node mapping.

During the biopsy, your doctor will make a small incision (measuring about a half-inch or 1 centimeter) over the sentinel lymph node. The lymph node is then removed through this incision and sent to a pathologist for testing.

Does a lymph node biopsy hurt?

Your doctor or the technician performing your sentinel node mapping procedure may inject a numbing solution along with the radioactive material that traces your lymph flow.

Your surgeon will also likely use at least topical anesthetics during the biopsy, in some cases, general anesthesia may be used.

So you’re unlikely to feel anything during the biopsy.

After your biopsy, you may notice some tenderness or soreness at the biopsy site. This can be followed by numbness and tingling as the incision heals.

Over-the-counter pain relievers like ibuprofen or acetaminophen are usually sufficient to manage this pain, but your doctor may prescribe you prescription pain relief, too.

If the result of your sentinel node biopsy is negative, this means that no cancer cells were found in the biopsied lymph node. This is a good sign that your cancer hasn’t spread to nearby lymph nodes or other organs.

A positive result on your biopsy means that the pathologist found cancer cells in the lymph node. This usually indicates that your cancer has spread from its original location to the sentinel lymph node and possibly other lymph nodes or organs.

The results of your sentinel lymph node biopsy will help your doctor determine the stage of your cancer and develop an appropriate treatment plan.

The results of your lymph node biopsy may also be done at the same time as the removal of a primary tumor, and your doctor may decide to remove more than one lymph node for testing.

When several lymph nodes are removed for testing, it’s called a lymph node dissection.

There’s a chance your doctor will not be able to identify a sentinel lymph node. But mapping is about 90 percent accurate in identifying the sentinel node, with only about a 10 percent false-positive rate.

Living with cancer

Sentinel node mapping and biopsy are some of the first steps in your cancer treatment plan. This procedure is only done if a primary cancer site has been identified or is strongly suspected.

Make sure you talk with your doctor about any concerns or questions you may have about things like:

  • staging
  • your specific type of cancer
  • your treatment plan
  • support services
  • counseling and therapy services

A cancer diagnosis can be overwhelming. Taking care of your physical, mental, and emotional health will all be important parts of your treatment plan and recovery.

Your doctor will be able to help you find local or online support groups where you can share experiences and ask questions of other people who have the same type of cancer.

You may also find it helpful to see a therapist regularly as a part of your support system.

Identifying a sentinel node is the first step your doctor will take to learn whether your cancer has spread.

If you’ve been diagnosed with cancer, the presence of cancer cells in this lymph node can signal a spread from your original cancer. This information will help your doctor stage your cancer and come up with a treatment plan.

Confronting a new cancer diagnosis can be scary. But a sentinel node biopsy is one tool that will be used to help understand more about your cancer and find you the best possible treatment options as early as possible.