Sentinel Lymph Node Biopsy

Test Overview

A sentinel lymph node biopsy is a surgery that takes out lymph node tissue to look for cancer. A sentinel node biopsy is used to see if a known cancer has spread from the original cancer site. A sentinel node biopsy may be done instead of a more extensive surgery called lymph node dissection. But if cancer is found in the sentinel lymph node at the time of surgery, more surgery may be needed to remove additional lymph nodes.

The sentinel lymph node is the first node in a group of nodes in the body where cancer cells may move to after they have left the original cancer site and started to spread. For example, the sentinel node (SN) for breast cancer is normally one of the lymph nodes under the arm.

Your doctor injects a blue dye or special tracer substance or both into the area around the original cancer site. The dye or tracer moves to the first lymph node (sentinel node) that drains close to the cancer site. The dye or tracer makes a map pattern of lymphatic fluid. The map can show where the cancer is likely to spread and which lymph node is most likely to have cancer cells. Your doctor can see the dye or tracer with a special device. The lymph node can be taken out, cut into very thin slices, and looked at under a microscope at the time of surgery. If a sentinel node is positive for cancer cells, more surgery may be needed to remove more lymph nodes.

Other tests, such as a culture, genetic tests, or immunological tests, may be done on the lymph node sample.

Why It Is Done

A sentinel lymph node biopsy is done to:

  • See if a known cancer, such as breast cancer or melanoma, has spread to the lymph nodes.
  • Remove a few lymph nodes instead of removing all the lymph nodes in an area. If the sentinel lymph node does not have cancer, this surgery takes less time, is simpler to do, and has a lower chance of long-term problems, such as ongoing swelling of an arm or leg (lymphedema).

How To Prepare

  • Follow the instructions exactly about when to stop eating and drinking. If you don't, your test may be canceled. If your doctor told you to take your medicines on the day of the test, take them with only a sip of water.
  • Be sure you have someone to take you home. Anesthesia and pain medicine will make it unsafe for you to drive or get home on your own.
  • Tell your doctor ALL the medicines, vitamins, supplements, and herbal remedies you take. Some may increase the risk of problems during your test. Your doctor will tell you if you should stop taking any of them before the test and how soon to do it.
  • If you take aspirin or some other blood thinner, ask your doctor if you should stop taking it before your test. Make sure that you understand exactly what your doctor wants you to do. These medicines increase the risk of bleeding.

How It Is Done

You will need to take off clothing near the biopsy site. You will wear a gown for a covering during the test.

Before a sentinel node biopsy is done, a dye, a tracer, or both are injected into the area. The dye stains the sentinel lymph node or nodes so they can be easily seen. The dye may turn your skin blue for a few days after the biopsy. The tracer travels to the sentinel lymph node where it can be detected.

You will be given anesthesia to make you sleep. Or the anesthesia may just numb the area being worked on. The lymph node or nodes are removed. You will have some stitches and a bandage over the biopsy site. The lymph nodes will be looked at under a microscope for cancer.

You will be watched by a nurse in the recovery room until you are fully awake.

How long the test takes

  • The biopsy usually takes 30 to 60 minutes. It may take longer if you have surgery to remove the cancer at the same time.

How It Feels

You will feel only a quick sting from the needle if you have a local anesthesia to numb the biopsy area. If you have a core needle biopsy, you may feel some pressure when the biopsy needle is put in.

You may have general anesthesia if your lymph node biopsy is part of a larger surgery. If so, you won't feel your biopsy at all.

Risks

It is possible to have some problems after a biopsy. Your doctor will give you instructions on what to do if a problem occurs. Risks include:

  • Bleeding from the biopsy site. This risk is higher for people who have bleeding problems or who take blood-thinning medicines. If you are at risk for bleeding, you may be given blood clotting factors before the biopsy.
  • Skin numbness at the biopsy site.
  • Infection at the biopsy site.
  • Swelling and fluid buildup (lymphedema). This is less likely after a sentinel node biopsy than if more lymph nodes are taken out (dissection).
  • Problems from general anesthesia, if it is used.
  • Damage to nerves at the biopsy site. This may cause weakness or pain.

Results

Test results are usually available within a few days.

The lymph node tissue is usually treated with special dyes (stains) that color the cells so problems can be clearly seen.

Sentinel lymph node biopsy

Normal

The dye or tracer flows evenly to the sentinel lymph node.

The lymph node has normal numbers of lymph node cells.

The structure of the lymph node and the cells look normal.

No cancer is present.

Abnormal

The dye or tracer does not flow evenly to the sentinel lymph node.

The sentinel lymph node cannot be identified.

Cancer cells may be seen. Cancer cells may start in the lymph nodes, such as in Hodgkin lymphoma. Cancer cells may have spread, or metastasized, from other sites, such as in breast cancer or melanoma.

If the sentinel lymph nodes do not have cancer, no other nodes will need to be taken out.

If the nodes contain cancer cells, more nodes may need to be removed.

Credits

Current as of: December 17, 2020

Author: Healthwise Staff
Medical Review:
Sarah Marshall MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Elizabeth T. Russo MD - Internal Medicine
Laura S. Dominici MD - General Surgery, Breast Surgical Oncology

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