Sentinel Node Biopsy


What is a sentinel node biopsy?

A sentinel node biopsy (also called a sentinel lymph node biopsy or SLNB) is a surgical procedure for people with cancer. During this procedure, the healthcare provider removes the sentinel nodes and sends them to a lab to test for cancer cells.

Sentinel nodes are the first lymph nodes where cancer cells might spread from a tumor. Lymph nodes are small organs that “filter” fluid in the body and help protect you from illness.

The word “sentinel” means a guard or someone keeping watch.

Why do providers perform a sentinel node biopsy?

Healthcare providers usually use a sentinel node biopsy to assess breast cancer or melanoma (a type of skin cancer). Sentinel node biopsy results help healthcare providers know if the cancer has spread beyond the original (primary) tumor. When certain cancers spread, they usually spread to the sentinel nodes first.

When is a sentinel node biopsy performed?

A sentinel node biopsy is part of a process called staging. During staging, healthcare providers determine whether the cancer has spread to the lymph nodes and how advanced the cancer is. Different cancer stages require different treatments.

Healthcare providers usually perform this test while they’re removing the original (primary) tumor, but not always. Sometimes, healthcare providers do a sentinel node biopsy before or after removing the primary tumor.

What are lymph nodes?

Lymph nodes are bean-shaped glands (organs) that do many important jobs. Immune cells inside lymph nodes attack bacteria that can make you sick. Lymph nodes also filter lymphatic fluid (lymph) throughout the body. Lymphatic fluid is liquid waste that drains from tissues and cells.

You have about 600 lymph nodes throughout your body. They are part of the lymphatic system, a central part of your immune system.

What are sentinel nodes?

Sentinel nodes are simply the first nodes draining a cancerous region. For breast cancer, they are usually located in the armpit. That’s why healthcare providers test the sentinel nodes to see if cancer has spread beyond the original tumor.

If there’s no sign of cancer in the sentinel nodes, it’s unlikely that cancer has spread to other lymph nodes. If the test detects cancer cells in the sentinel nodes, your provider may recommend removing other lymph nodes to check for cancer.

Test Details

What should I expect during the test?

Several hours before the procedure, you will receive a safe radioactive substance (tracer) in your vein which will lead the surgeon to the sentinel lymph node(s). When it is time for the actual procedure you’ll receive general anesthesia through an IV (a needle in your arm). The medicine will put you to sleep during the procedure.

Once you’re asleep, your healthcare provider:

  • Injects blue dye in or around the tumor. Often, providers use both the dye and the radioactive tracer.
  • The dye stains the sentinel node blue so your healthcare provider can see it. If you received a radioactive substance, your healthcare provider will use an instrument called a gamma detector to locate the sentinel node.
  • Makes a small incision (cut) and removes the sentinel node or nodes. Most of the time, providers remove between one and five sentinel nodes.
  • Closes the incision and secures it with surgical tape, stitches or surgical glue.
  • Sends the sentinel nodes to a lab to check for cancer cells.

What should I expect after the test?

After the procedure, you can expect to be sore near your incision. Talk to your healthcare provider about taking over-the-counter or prescription pain medication while your incision heals. The area may be tender for several days following the procedure. Your arm may feel stiff if the sentinel node was in your armpit.

Ask your healthcare provider when you can return to your regular activities. Most people need to wait several weeks before running, exercising or lifting. You’ll need to keep your incision clean and give it time to heal.

What are the benefits of this test?

A sentinel node biopsy allows your provider to stage cancer accurately. It may also help you avoid unnecessary surgery.

If cancer cells aren’t in the sentinel nodes, it’s highly unlikely that cancer has spread to other lymph nodes or parts of the body. Your provider won’t need to remove other lymph nodes.

What are the risks of this test?

Generally, a sentinel node biopsy is a safe procedure. But every surgery has some risks. Sentinel node biopsy risks 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 contrast dye providers use to locate the sentinel node.
  • Lymphedema: This condition happens when the lymph nodes are damaged. If lymphatic fluid (lymph) can’t flow through the lymph nodes, excess fluid builds up in the body’s soft tissues. The fluid buildup causes swelling and pain. Lymphedema occurs more often when providers remove several lymph nodes.

Results and Follow-Up

When should I know the biopsy results?

Your healthcare provider will usually give you the results of the biopsy within a week. If your healthcare provider needs to discuss results with your cancer care team, it may take longer to receive results. Depending on the results, your provider will arrange follow-up cancer care, recommend additional treatments and monitor your health through regular checkups.

If you have breast cancer that has spread to the sentinel nodes, your healthcare provider may recommend a procedure called axillary lymph node dissection (ALND). During an ALND, your healthcare provider removes more lymph nodes (usually around 20). A lab tests the nodes for cancer cells.

When should I call my healthcare provider?

Following a sentinel node biopsy, call your healthcare provider if you have:

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

Additional Details

Providers most often use a sentinel node biopsy to tell whether breast cancer or melanoma has spread beyond the original tumor. A sentinel node biopsy can also help stage cancer of the penis or uterine cancer (endometrial cancer).

Researchers and healthcare providers are studying this test to see if they can use it to stage other cancers as well, including:

If you have cancer, a sentinel node biopsy gives your healthcare provider essential information about the disease stage. The risks of this surgical procedure are low, and most people recover quickly. This important test reveals if cancer has spread beyond the original tumor. It may also help you avoid unnecessary surgery. Your healthcare provider will use the results from this test to plan the most effective treatment for you.

Last reviewed by a Cleveland Clinic medical professional on 12/10/2020.


· AIM at Melanoma Foundation. What is a Sentinel Lymph Node Biopsy? ( Accessed 12/7/2020.

· American Cancer Society. Types of biopsies used to look for cancer. ( Accessed 12/7/2020.

· National Cancer Institute. Sentinel Lymph Node Biopsy. ( Accessed 12/7/2020.

· Susan G. Komen. Accessing Lymph Nodes. ( Accessed 12/7/2020.

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