Lymphatic Mapping with Sentinel Node Biopsy

This information will help you understand your lymphatic mapping with sentinel node biopsy procedure. You may have this procedure if you have breast cancer or melanoma so that your doctor can see if the cancer cells have spread to your lymph nodes.

Your Lymphatic System

Lymphatic fluid is the clear fluid that travels through the lymphatic system and carries cells that help fight infections and other diseases.

Lymphatic vessels are tiny vessels similar to blood vessels that carry lymphatic fluid throughout the body.

Lymph nodes are small bean-shaped structures located along the lymphatic vessels. The lymph nodes filter out bacteria, viruses, cancer cells and other waste products.

A sentinel lymph node (also known as a sentinel node) is the first lymph node(s) to which cancer cells are most likely to spread from a primary tumor.

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Lymphatic Mapping

Lymphatic mapping is the first step in a sentinel node biopsy. It’s done to find the sentinel node. The mapping procedure will take 1 to 2 hours, and you don’t need to do anything to prepare. You will be given an appointment for your mapping procedure.

On the day of your procedure, please go to:

  • Nuclear Medicine Department: 1250 First Avenue (between East 67th and East 68th Streets); elevator to 2nd floor
  • Presurgical Center (PSC): 1275 York Avenue (between East 67th and East 68th Streets); B elevator to 6th floor
  • Surgical Day Hospital (SDH): 1275 York Avenue (between East 67th and East 68th Streets); M elevator to 2nd floor

During your procedure


While you lie on an exam table, your doctor will inject a small amount of a radioactive fluid near the site of your cancer. During the injection, you might feel a stinging or burning sensation. The radioactive fluid will travel to the sentinel nodes so they can be seen later during your scan.


While you wait for your scan, you can either stay in the hospital or you can leave. For most patients, the waiting time is less than an hour, but it can vary. You must return on time for your scan, so be sure to note the time you’re told to return.

When it’s time for your scan, your technologist will take you to the scanning room. You will lie on a narrow table while he or she takes a series of pictures. Each picture takes 5 minutes, and you must lie very still during this time. If you feel uncomfortable staying in any position for 5 minutes, ask the technologist to count down the time for you. Ask your doctor if it’s ok to take pain medication before your scan. The scan will take 10 to 15 minutes.

The pictures taken during your scan will show the flow of the radioactive fluid and which lymph nodes absorbed it. This information will be used by your surgeon as a guide (or map) to determine the location of the sentinel node(s).

After your procedure

If you are having surgery the same day as your mapping procedure, you will be escorted from the scanning room to the operating room. In most other cases, you will go home after the mapping procedure.

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Sentinel Node Biopsy

Before your procedure

The sentinel node biopsy is a surgical procedure. Refer to the resource your nurse gave you called Getting Ready for Surgery, which explains how to prepare for the biopsy.

During your procedure

While you are asleep, your surgeon will inject a small amount of a blue dye near the site of your cancer. This dye will travel through your lymphatic fluid to the sentinel node(s), staining them blue. This allows your surgeon to see them.

To locate the sentinel node(s), your surgeon will use a small device to measure the radioactivity from the fluid that was injected during the mapping procedure. Once the sentinel node(s) are located, your surgeon will make a small incision (surgical cut). The sentinel nodes will be blue from the blue dye, allowing your surgeon to see them. He or she will remove the sentinel node(s) and send them to the Pathology Department to see if they contain cancer cells.

If there are cancer cells in your sentinel node(s), your surgeon can do a lymph node dissection right away or at a later date. During a lymph node dissection, your surgeon removes the lymph nodes that contain cancer cells. Your doctor will talk with you about the timing that is right for you.

After your procedure

You may go home that same day or you may need to stay in the hospital, depending on any additional surgeries you may have had.

More tests will be done on your sentinel node(s) in the Pathology Department. Depending on the results, more lymph nodes may need to be removed. Your doctor will talk with you about this in detail.


Please refer to the resource Caring for Yourself After Your Sentinel Lymph Node Biopsy for information about what you can expect after your procedure.

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