Sentinel Lymph Node Biopsy

Procedure overview

A sentinel lymph node biopsy is a procedure to see if or how far a cancer has spread.

Lymph nodes are part of the body’s lymphatic system. This system is one way your body fights bacteria, viruses, and other foreign germs. Inside the lymph system is a clear fluid called lymph. The fluid traps these germs. This fluid flows to your lymph nodes. Lymph nodes are small, round organs. They are in your neck, underarms, groin, belly (abdomen), and chest. If you have an infection, nearby lymph nodes may swell. They can also become hard and painful. The same symptoms can happen if cancer cells spread to a lymph node. Or in some cases, cancer cells may be in a lymph node and not cause symptoms.

The sentinel lymph node is the node that cancer cells may go into first, before going to other nodes. Looking at cells in this node can give your healthcare provider a lot of information about your cancer. To do this, your healthcare provider may order a procedure called a sentinel lymph node biopsy. The biopsy is done with a surgery to remove the node so that it can be examined.

Reasons for the procedure

The main reason for a sentinel lymph node biopsy is to see if the cancer has spread beyond the main tumor. This will help determine the best kinds of treatment for you.

It is an alternative to standard lymph node removal. In that procedure, more lymph nodes are removed from the area near the cancer. This is done whether or not they may have cancer cells. With a sentinel lymph node biopsy, more lymph nodes are removed only if there is cancer in the sentinel node. If the sentinel node does not have cancer cells, other nodes don't need to be removed.

A sentinel lymph node biopsy is most often used in cases of breast cancer or melanoma.

Risks of the procedure

Sentinel lymph node biopsy is called a minimally invasive procedure. This means the risks are less than having more nodes removed.

All surgeries have some risks. The most common risks of this procedure include:

  • Pain and swelling at the site of the biopsy

  • Bruising at the site of the biopsy

  • Not enough lymph fluid draining from the area

  • A pocket of lymph fluid, called a seroma

  • Allergic reaction to the contrast dye that is used to help find the sentinel lymph node

  • Short-term reactions to the dye, such as discolored urine or stains on the skin

Your own risks may vary according to your age, your general health, and the reason for your procedure. Talk with your healthcare provider to find out what risks may apply to you.

Before the procedure

Tell your healthcare provider if you:

  • Are pregnant or think you may be pregnant

  • Are taking any medicines, vitamins, or herbs

  • Have any allergies, especially to anesthesia or medical dye

  • Have a history of bleeding problems

  • Are taking a blood-thinning medicine, such as aspirin or warfarin

  • Had a biopsy in the past

  • Had radiation treatment to the biopsy site


  • Ask a family member or friend to take you home from the hospital. You can’t drive yourself if you are given sedation during the procedure.

  • Follow any directions you are given for not eating or drinking before surgery.

  • Follow all other instructions from your healthcare provider.

During the procedure

You usually will have a sentinel lymph node biopsy done as an outpatient. This means you go home the same day. In some cases, you may need to stay overnight. The procedure often takes about 30 to 60 minutes. This is how the biopsy is often done:

  1. You may get a sedative medicine to help you relax.

  2. You may get local or general anesthesia. 

  3. The surgeon will inject a special substance near the site of the tumor. This substance travels to the sentinel lymph node. It may be a tiny amount of radioactive material. Or it may be a blue dye. In some cases, both may be used. 

  4. The surgeon then uses a scanner to find the lymph node that contains the substance or the dye. This is the sentinel lymph node. Sometimes there can be more than 1 node.

  5. The surgeon will make a small cut (incision) in the skin near the node. He or she will remove the node.

  6. The biopsy site will then be closed and covered with a bandage.

After the procedure

After the biopsy, you may feel some pain at the site of the surgery. You may be drowsy if you had anesthesia. Your healthcare provider will likely give you pain medicine. Pain should stop after a few days. You may have a little bleeding at the site of the biopsy. This is normal.

Call your healthcare provider if you have any of these:

  • Swelling at the biopsy site

  • Pain or redness at the site that gets worse

  • Bleeding from the site that gets worse

  • Fluid (pus) leaking from the site

  • Fever

  • Other symptoms as advised

After the biopsy, the lymph node is sent to a doctor called a pathologist. He or she cuts it into small pieces and looks at these with a microscope to check for cancer cells. Your medical team will tell you the results of your biopsy. Then your team will talk with you about your treatment plan. In many cases, more lymph nodes will need to be removed. This is most often done in a follow-up procedure. But in some cases, the pathologist can work quickly and more lymph nodes can be removed during your first procedure.

Online Medical Reviewer: Hanrahan, John, MD
Online Medical Reviewer: Levy, Adam S, MD
Date Last Reviewed: 1/1/2021
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