Sentinel Node Biopsy

A sentinel node biopsy is a procedure to test if cancer has spread beyond the original tumor. It’s most commonly used in people with breast cancer and melanoma. During the procedure, healthcare providers remove small organs called sentinel nodes and test them for cancer cells. The results help providers determine the most appropriate treatments.


Sentinel lymph nodes inside the breast and armpit
A sentinel node biopsy can show if cancer cells have spread from the primary tumor.

What is a sentinel node biopsy?

A sentinel node biopsy (sentinel lymph node biopsy) is a surgical procedure for people with cancer. During the procedure, a healthcare provider removes one or more sentinel nodes and sends them to a lab to test for cancer cells. The results show if cancer has spread beyond the original (primary) tumor.

Your lymph nodes are small, bean-shaped glands that filter fluid in your body and help protect you from illness. You have about 600 lymph nodes throughout your body. They trap harmful substances, including viruses, bacteria and cancer cells.

Sentinel nodes are the first lymph nodes where cancer cells might spread from a tumor. This is why providers test your sentinel nodes for signs of cancer spread.

When is a sentinel node biopsy performed?

Providers primarily use sentinel node biopsy during cancer staging in breast cancer and melanoma. Cancer staging allows providers to determine whether cancer is spreading and how advanced it is. A sentinel node biopsy can also help stage penile or uterine cancer (endometrial cancer).

Researchers and healthcare providers are researching whether they can use it to stage other cancers as well, including:

Healthcare providers usually perform this procedure while they’re removing the tumor. Sometimes, healthcare providers do a sentinel node biopsy before or after removing the primary tumor.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Test Details

How does a sentinel node biopsy work?

Before a sentinel lymph node biopsy, a provider will inject a special dye around the cancer site to determine which lymph nodes are the main draining lymph nodes. This means that if the cancer were to spread, it would spread to these lymph nodes first.

During a sentinel node biopsy, a surgeon locates your sentinel nodes, removes them and sends them to a lab for testing. A different provider tests the nodes for cancer cells.

How do I prepare for a sentinel node biopsy?

Follow your healthcare provider’s guidance on how to prepare. You may receive instructions related to:

  • Fasting: When (and what foods or drinks) you should stop eating and drinking prior to the surgical procedure.
  • Medications: Which medicines, vitamins, herbs or supplements you should stop taking.

Arrange to have someone drive you home on the day of your procedure.

What should I expect during the procedure?

Before or during surgery, you may receive an injection of a safe radioactive substance (tracer) and/or a dye that travels the same path that fluid draining from your tumor would take. The tracer leads your surgeon to your sentinel lymph node(s).

You’ll receive general anesthesia through an IV (a needle in your arm) that will put you to sleep so you don’t feel any pain. Once you’re asleep, your healthcare provider will:

  1. Locate your sentinel lymph node(s). If you received a tracer, your healthcare provider will use an instrument called a gamma detector to locate the sentinel node. They may inject a blue dye near the tumor site that stains your sentinel nodes blue or a fluorescent dye. Often, providers use both the dye and the tracer.
  2. Remove the lymph node(s). Providers make an incision (cut) and remove one or more sentinel nodes.
  3. Close the incision. Your provider will use stitches to close the incision.

Afterward, they’ll send the sentinel nodes to a lab, where a pathologist will test for cancer cells. A pathologist is an expert in diagnosing medical conditions using lab tests.

How many nodes are taken in a sentinel node biopsy?

It depends. Your healthcare provider will remove enough sentinel nodes to accurately detect cancer cells. Most providers remove more than one, but the ideal number is debatable. Some studies show that removing three sentinel nodes is often enough to detect cancer. Other research shows that up to five may need to be removed for an accurate diagnosis.

The numbers vary for every person based on their unique case.

What should I expect after the procedure?

Many people have someone drive them home the same day, but you may need to stay in the hospital overnight. Follow your healthcare provider’s advice on when it’s safe to leave.

As you heal, you can expect the following, which are all normal:

  • Soreness or tenderness near your incision site.
  • Tingling and numbness. (This is your nerves healing.)
  • Blue or green pee (urine) or stool from the dye.
  • Bluish color near the incision site from the dye.
  • Hardening beneath the tissue where scar tissue is forming.
  • Stiffness in your arm (if your provider removed sentinel nodes from your armpit).

Before leaving the medical facility, ensure you know how to care for the incision site and understand what potential complications to look out for. Ask when it’s safe to return to your regular activities. Recovery time for a sentinel node biopsy varies, but most people need to wait several weeks before running, exercising or lifting.

What are the risks of a sentinel node biopsy?

A sentinel node biopsy is a safe procedure. Still, every surgery poses some risks. Potential side effects and complications include:

  • Problems at the incision site. Bleeding, bruising, swelling and pain can occur at the incision site. The incision can also become infected. Signs of infection include redness, swelling and fever.
  • Allergic reaction. Rarely, some people are allergic to the blue dye providers use to locate the sentinel node.
  • Lymphedema. Lymph node removal can cause the fluid that normally flows through your lymph nodes to build up, causing swelling and pain. Lymphedema is a rare complication that occurs most often when providers remove several lymph nodes, not just select sentinel lymph nodes. Typically, providers leave behind enough lymph nodes so that fluid continues to drain normally.
  • Axillary web syndrome (AWS). With AWS, or “cording,” you may notice multiple cord-like structures underneath the skin on your inner arm. Although it’s rare, cording may occur if a provider removes lymph nodes from your armpit. The cords may form days, weeks or months after surgery.

Contact your healthcare provider immediately if you notice signs of these complications.


Results and Follow-Up

What type of results do you get, and what do the results mean?

Results are either positive or negative. A negative result means that there’s no sign of cancer in your sentinel nodes. It’s unlikely that cancer has spread to other lymph nodes. Positive results mean that the biopsy did detect cancer cells in your lymph node(s).

If your results come back positive, your healthcare provider may recommend removing other lymph nodes (not just sentinel nodes) to check for cancer spread. They may recommend additional treatments. Your healthcare provider will advise you on the next steps based on your unique diagnosis.

How long does it take to get sentinel node biopsy results?

You may receive results as soon as that same day, or it may take up to a few weeks. If your test results come back positive that same day, your healthcare provider may remove more lymph nodes for testing. That way, you don’t have to return for surgery. It may take longer to receive results if the surgeon needs to discuss results with your cancer care team.

When should I call my healthcare provider?

Call your healthcare provider if you have any signs of a complication, including:

  • Fever.
  • Swelling, warmth or redness near the incision site.
  • Bleeding from the incision.
  • Pain that doesn’t get better with pain medication.


Additional Common Questions

How painful is a sentinel node biopsy?

You won’t feel any pain during the procedure, as you’ll be asleep. Most people manage pain in the days after with over-the-counter medicines and icing the area. Few may need prescription pain medications. Talk to your healthcare provider about medicine to help with the pain while your incision heals.

A note from Cleveland Clinic

A sentinel node biopsy provides essential information about how advanced your cancer is. The risks of this surgical procedure are low, and most people recover quickly. If cancer cells aren’t in your sentinel nodes, it’s a good sign that cancer hasn’t spread beyond your tumor site. Positive results provide important information your healthcare provider can use to plan the most effective treatment for you.

Medically Reviewed

Last reviewed on 09/08/2023.

Learn more about our editorial process.

Cancer Answer Line 866.223.8100