Sentinel node biopsy is a procedure to see if cancer has spread. It can tell whether the cancer cells have broken away from where they started and spread to the lymph nodes. Sentinel node biopsy is often used in people who have breast cancer, melanoma and other types of cancer.

The sentinel nodes are the first few lymph nodes to which cancer spreads. In sentinel node biopsy, a tracer material is used to help the surgeon find the sentinel nodes during surgery. The sentinel nodes are removed and tested in a lab.

If the sentinel nodes are free of cancer, then cancer probably hasn't spread. This means that removing additional lymph nodes is not necessary. More surgery might not be needed.

If a sentinel lymph node biopsy shows cancer, you might need to have more lymph nodes removed for testing.

Why it's done

Sentinel node biopsy is used to see whether the cancer cells have spread to the lymph nodes. The lymph nodes are part of the body's germ-fighting immune system. Lymph nodes are found throughout the body. If cancer cells break away from where they started, they often spread to the lymph nodes first.

Sentinel node biopsy is routinely used for people with:

  • Breast cancer.
  • Endometrial cancer.
  • Melanoma.
  • Penile cancer.

Sentinel node biopsy is being studied for use with other types of cancer, such as:

  • Cervical cancer.
  • Colon cancer.
  • Esophageal cancer.
  • Head and neck cancer.
  • Non-small cell lung cancer.
  • Stomach cancer.
  • Thyroid cancer.
  • Vulvar cancer.


Sentinel node biopsy is generally a safe procedure. But as with any surgery, it carries a risk of complications, including:

  • Bleeding.
  • Pain or bruising at the biopsy site.
  • Infection.
  • Allergic reaction to the dye used for the procedure.
  • Fluid buildup and swelling in lymph vessels, which is called lymphedema.


Lymphedema is an unlikely complication of sentinel node biopsy. Lymphedema is more likely to happen if many lymph nodes are removed from one area.

Because only a few lymph nodes are removed in sentinel node biopsy, the risk of lymphedema is small. Dozens of other lymph nodes remain in the area where the sentinel node biopsy is done. Typically, those remaining lymph nodes can take over for the lymph nodes that are removed.

How you prepare

You might need to stop eating and drinking for a period of time before the procedure. This is to avoid complications from the medicine used to put you in a sleep-like state during surgery. Ask your health care team for specific instructions.

What you can expect

Before the procedure

The first step in a sentinel node biopsy is to find the sentinel nodes. Options include:

  • Radioactive solution. In this option, a weak radioactive solution is injected near the cancer. This solution is taken up by the lymphatic system and travels to the sentinel nodes.

    This injection is usually done several hours or the day before the surgical procedure to remove the sentinel nodes.

  • Blue dye. In this option, a harmless blue dye is injected into the area near the cancer. The dye travels to the sentinel nodes, staining them bright blue.

    You might notice a change in your skin color at the injection site. This color usually goes away, but it can be permanent. You also might notice that your urine is blue for a brief time.

    The blue dye is typically injected just before the sentinel node biopsy.

Whether you receive the radioactive solution or the blue dye or both to locate the sentinel nodes is usually determined by your surgeon's preference. Some surgeons use both techniques in the same procedure.

During the procedure

You're likely to be given medicine to put you in a sleep-like state during the procedure.

The surgeon begins by making a small incision in the area over the lymph nodes.

When radioactive solution is used before the procedure, radioactivity builds up in the sentinel nodes. The surgeon uses a small hand-held instrument called a gamma detector to find the spots where the radioactivity has built up. The lymph nodes with the most radioactive solution are the sentinel nodes.

If the blue dye is used, it stains the sentinel nodes bright blue so the surgeon can see them.

The surgeon then removes the sentinel nodes. Typically, there are a few sentinel nodes, and all are removed. The sentinel nodes are sent to a lab where they are examined under a microscope for signs of cancer.

Often the sentinel node biopsy is done at the same time as surgery to remove the cancer. Or sentinel node biopsy can be done before or after surgery to remove the cancer.

After the procedure

You may be moved to a recovery room where your health care team watches for complications from the procedure. If you don't need additional surgery, you may be able to go home the same day.

How soon you can return to your regular activities depends on your situation. Ask your health care team what you can expect.

If you have sentinel node biopsy as part of a procedure to remove the cancer, your hospital stay will be determined by your health care team.


If the sentinel nodes don't show cancer, you won't need to have more lymph nodes removed and tested. If further treatment is needed, information from the sentinel node biopsy is used to develop your treatment plan.

If any of the sentinel nodes contain cancer, you might need to have more lymph nodes removed. This allows your health care team to find out how many are affected.

Sometimes, the sentinel nodes are tested right away during the sentinel node biopsy. If the sentinel nodes show cancer, you might have more lymph nodes removed right away rather than having another surgery later.