Breast Cancer Sentinel Lymph Node Biopsy

Medically reviewed by Drugs.com. Last updated on Jun 30, 2025.

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What do I need to know about a sentinel lymph node biopsy (SLNB)?

A breast cancer SLNB is used to see if cancer has spread in your body. Cancer spreads first to sentinel lymph nodes. Breast cancer sentinel lymph nodes are usually found in the armpit, but they may be along the sternum (breastbone) or collarbone. A biopsy is a procedure to remove the lymph nodes so they can be tested for cancer. Your healthcare provider will use the results of your SLNB to plan tests or treatment, if needed.

How do I prepare for a SLNB?

• You may need a nuclear scan before your procedure. During a nuclear scan, healthcare providers will inject a small amount of radioactive liquid in your breast. Radioactive liquid will move to the location of your lymph nodes and help them show up better in pictures. A camera will take pictures of the lymph nodes. The pictures will help your healthcare provider plan for your procedure.
• Your healthcare provider will talk to you about how to prepare for your procedure. You may be told not to eat or drink anything after midnight on the day of your procedure. Your provider will tell you which medicines to take or not take on the day of your procedure. You may be given contrast liquid during your biopsy. Tell your provider if you have ever had an allergic reaction to contrast liquid. Arrange for someone to drive you home and stay with you after your procedure.

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What will happen during a SLNB?

• You may be given an antibiotic through your IV to help prevent a bacterial infection. Tell the healthcare provider if you have ever had an allergic reaction to an antibiotic. You may be given general anesthesia to keep you asleep and free from pain during your procedure. You may instead be given local anesthesia to numb the area. With local anesthesia, you may still feel pressure or pushing during the procedure, but you should not feel any pain.
• Your healthcare provider will inject blue contrast liquid, radioactive liquid, or both near the tumor. The liquid will move to the SLN. Your provider may move an instrument over your skin that will show pictures of the SLN on a monitor. Your provider will make a small incision in the skin that covers the SLN. The SLN will be removed and checked for cancer cells. If cancer is found, your provider may remove several more lymph nodes for testing. Your incision may be closed with stitches or strips of medical tape and covered with a bandage.

What should I expect after a SLNB?

• Healthcare providers will monitor you until you are awake. You may be able to go home after you are awake and your pain is controlled.
• Your urine or bowel movement may be blue for 24 to 48 hours after your procedure. This is caused by the blue contrast liquid given to you during the procedure.
• You may have bruising or swelling at the biopsy site. This is normal and expected.
• The arm closest to the biopsy site may be sore. This should get better within 48 to 72 hours.

What are the risks of a SLNB?

You may bleed more than expected or get an infection. You may develop lymphedema (swelling from lymph fluid buildup) in the arm nearest to where the SLN was removed. You may have long-term pain or discomfort in your arm. Your skin may be permanently thick or hard. Your nerves may be damaged during your procedure. This may cause numbness, tingling, or trouble moving your arm.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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