What is a sentinel lymph node biopsy?

A sentinel lymph node biopsy (SLNB) is a surgical procedure that checks your lymph nodes for cancer cells. An SLNB is only done if you have already been diagnosed with cancer. This procedure finds, removes, and checks the sentinel lymph node to determine the stage of your cancer. Cancer staging is usually based on the size of your tumor and whether the cancer has spread (metastasized) to nearby areas, lymph nodes, or other parts of your body. Knowing the stage of your cancer can help your health care provider plan the best treatment for you.

Your lymph nodes are located throughout your body, including your underarms, neck, chest, abdomen (belly), and groin. They are part of the lymphatic system, which helps to protect you from illness and maintain healthy fluid levels in your body. 

Your lymphatic system is part of your body’s immune system. Your lymph fluid carries fluid and cells throughout your body to help fight infections. It may also filter cancer cells (if there are any). But sometimes, with certain cancers such as breast cancer and melanoma (the most serious type of skin cancer), some cancer cells may spread to your lymph nodes. 

Cancers spread when cells break off from the original (primary) tumor and are carried by the lymphatic system to other parts of your body. The sentinel lymph node is the first lymph node where these types of cancers are most likely to spread. It’s usually located near the original tumor site and may receive drainage from the tumor. Your provider tests your sentinel lymph node to see if your cancer has spread. Sometimes, you may have more than one sentinel lymph node. 

Other names: lymph node biopsy, sentinel node biopsy, sentinel lymph node mapping and biopsy

What is it used for?

A sentinel lymph node biopsy is used to find out whether an early-stage cancer has spread through your lymphatic system to your lymph nodes or other parts of your body. It’s most often used for people who have breast cancer or melanoma and is usually done when the tumor is being removed.

Why do I need a sentinel lymph node biopsy?

You may need this test if you've been diagnosed with breast cancer, melanoma, or certain other types of cancer. It can show whether your cancer is spreading and help your provider create the best treatment plan for you.

What happens during a sentinel lymph node biopsy?

A sentinel lymph node biopsy may be done in a hospital or an outpatient surgical center. The procedure usually includes a special type of imaging test called lymphoscintigraphy. Lymphoscintigraphy may also be called lymph node mapping. It is the process of taking pictures of your lymphatic system to locate the sentinel lymph node. The procedure includes the following steps:

• Your provider will apply medicine to numb the skin over the procedure area.
• You will be injected with a small amount of a radioactive substance called a tracer near the tumor. The tracer will travel and collect in the sentinel lymph node, or nodes. You may also be injected with a blue dye that stains the lymph node, making it easier to see.
• You will be given general anesthesia. General anesthesia is a medicine that makes you unconscious. It makes sure you won't feel any pain during the surgery. A specially trained doctor called an anesthesiologist will give you this medicine.
• Once you’re unconscious, a camera will take images of the area. The camera finds and records the location of the tracer, which will have settled in the sentinel node.
• The node will be removed and sent to a lab, where it will be checked for cancer cells. This part of the test is known as a biopsy.
• The original tumor is also usually removed during the procedure.

Will I need to do anything to prepare for the test?

You will probably need to fast (not eat or drink) for several hours before the test. You may also need to stop taking blood thinners, such as aspirin, for a certain time before your test. Your provider will let you know when you need to stop taking your medicine and anything else to do to prepare for the test.

In addition, be sure to arrange for someone to take you home. You may be groggy and confused after you wake up from the procedure.

Are there any risks to the test?

• You may have a little bleeding, pain, or bruising at the biopsy site.
• There is also a small risk of infection, which can be treated with antibiotics.
• Allergic reactions to the tracer are rare and usually mild.
• If only the sentinel lymph node is removed, there is a low risk of lymphedema (swelling, usually of the arms or legs) from the lymph fluid. The risk increases with the number of lymph nodes removed.

There is very little exposure to radiation in a sentinel lymph node biopsy. While radiation exposure from the tracer in a sentinel lymph node biopsy is safe for most adults, it can be harmful to a developing baby. So be sure to tell your provider if you are pregnant or think you may be pregnant.

What do the results mean?

The results will be given as positive or negative.

If your results are positive, it means cancer was found in the sentinel lymph node and may have spread to nearby lymph nodes and/or other organs. Your provider may recommend removing and testing more lymph nodes to check for cancer cells.

If your results are negative, it means no cancer cells were found in the sentinel lymph node, and it's unlikely that the cancer has spread. You will not need to have any more lymph nodes removed.

If you have questions about your results, talk to your provider.

Is there anything else I need to know about a sentinel lymph node biopsy?

While sentinel lymph node biopsies are mostly used to stage breast cancer or melanoma, it is sometimes used for penile and uterine cancer. It is also being studied for use with other types of cancer, including:

• Colon cancer
• Stomach cancer
• Thyroid cancer
• Non-small cell lung cancer