Sentinel Lymph Node Biopsy

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…

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

Tell your doctor if you:

  • Are or might be pregnant.
  • Are taking any medicines, especially medicines for depression, such as paroxetine (Paxil), fluoxetine (Prozac), amitriptyline (Limbitrol), or venlafaxine (Effexor).
  • Are allergic to any medicines, including any anesthetics or dyes.
  • Take a blood thinner, or if you have had bleeding problems.
  • Have had a biopsy in the past.
  • Have had radiation treatment to the biopsy site.

Follow your doctor’s instructions carefully. If you are given a medicine (sedative) to make you relax or sleep before the biopsy, do not eat or drink for 8 hours before the biopsy. Arrange for someone to drive you home after the biopsy.

Talk to your doctor about concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).

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.

If you are very anxious about the biopsy, you may be given a medicine (sedative) to help you relax.

Before a sentinel node biopsy is done, the dye or tracer is injected into the area, and a special camera (lymphoscintigraphy) takes pictures of the lymph nodes. Some doctors use pain medicine with the dye to reduce discomfort. The dye may turn your skin blue for a few days after the biopsy.

The first lymph node or nodes to absorb the tracer are called the sentinel nodes. This node or nodes and the tissue around them are taken out. You may have a numbing medicine (local anesthesia) or go to sleep for the biopsy. The lymph node sample is cut into many thin slices and looked at under a microscope for cancer. You will have some stitches and a bandage over the biopsy site.

A sentinel lymph node biopsy usually takes 30 to 60 minutes but may take longer. If you have general anesthesia, you will be watched by a nurse in the recovery room until you are fully awake.

Your doctor will give you specific instructions to take care of your biopsy site. During your follow-up visit, your doctor will discuss the results of your biopsy with you and take out your stitches.

How It Feels

You may feel a sharp sting or burn from the medicine used to numb the biopsy site or from the dye or tracer. Feeling pressure or warmth during the biopsy is normal, but you should feel little or no pain. If you have pain, tell your doctor. If you feel like you are having an allergic reaction, tell your doctor. This can happen with the dye used for this biopsy.

If you have general anesthesia, you may feel drowsy for several hours after the biopsy. You may have a mild sore throat from the tube used to help you breathe during the biopsy. Throat lozenges and gargling with warm salt water may help soothe your sore throat. You may get medicine at the biopsy site that will help with the pain for 6 to 12 hours. You may have more pain after this medicine wears off.

The biopsy site may be sore for several days. A small amount of bleeding is normal. Ask your doctor how much drainage to expect. Call your doctor immediately if you have:

  • An increase in pain, redness, or swelling at the biopsy site.
  • A fever.
  • An increase in bleeding or drainage, such as pus.
  • Any swelling in your arm.


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

  • 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 (axillary dissection).
  • Problems from general anesthesia, if it is used
  • Damage to nerves at the biopsy site. This may cause weakness or pain.


A sentinel lymph node biopsy is a surgery that takes out lymph node tissue to look for infection or cancer. Test results from 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


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.


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.

What Affects the Test

You may not be able to have a sentinel lymph node biopsy if you:

  • Are pregnant.
  • Have inflammatory breast cancer.
  • Have breast cancer that has already spread throughout the breast and lymph nodes.

Also, experts don’t recommend sentinel lymph node biopsy for women who have DCIS and plan to have a lumpectomy.

What To Think About

  • In a sentinel lymph node biopsy, less tissue is taken out but more sections of tissue are looked at than by a standard lymph node dissection. But if cancer is found, additional surgery may be needed to look at more lymph nodes.
  • Swelling in the area around the biopsy site is less common with sentinel lymph node biopsy than with a lymph node dissection.
  • The dye may cause your skin to be blue for several days after the biopsy. It may also cause your urine to turn green for 1 to 2 days.
  • It is possible to have false-negative results from the small sample taken during a sentinel lymph node biopsy.


Other Works Consulted

  • American Cancer Society (2010). Breast Cancer: Treating Breast Cancer. Available online:
  • National Cancer Institute (2011). Sentinel Lymph Node Biopsy. Available online:
  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.


Current as ofDecember 19, 2018

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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