Date Updated: 11/10/2020


Sentinel node biopsy is a surgical procedure used to determine whether cancer has spread beyond a primary tumor into your lymphatic system. It's used most commonly in evaluating breast cancer and melanoma.

The sentinel nodes are the first few lymph nodes into which a tumor drains. Sentinel node biopsy involves injecting a tracer material that helps the surgeon locate the sentinel nodes during surgery. The sentinel nodes are removed and analyzed in a laboratory.

If the sentinel nodes are free of cancer, then cancer is unlikely to have spread, and removing additional lymph nodes is unnecessary.

If a sentinel lymph node biopsy reveals cancer, your doctor might recommend removing more lymph nodes.

Why it's done

Sentinel node biopsy is recommended for people with certain types of cancer to determine whether the cancer cells have spread into the lymphatic system.

Sentinel node biopsy is routinely used for people with:

  • Breast cancer
  • Melanoma

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

  • Colon cancer
  • Esophageal cancer
  • Head and neck cancer
  • Non-small cell lung cancer
  • Stomach cancer
  • Thyroid 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
  • Lymphedema — a condition in which the lymph vessels can't adequately drain lymph fluid from an area of your body, causing fluid buildup and swelling


Although lymphedema is an unlikely complication of sentinel node biopsy, one of the main reasons sentinel node biopsy was developed was to decrease the chance of developing lymphedema, which is more likely to occur if many lymph nodes are removed from one area.

Because only a few lymph nodes are removed, the risk of lymphedema after sentinel node biopsy is small. Dozens of other lymph nodes remain in the area of your body where the sentinel node biopsy is done. In most cases, those remaining lymph nodes can effectively process the lymph fluid.

How you prepare

Your doctor might ask you to avoid eating and drinking for a certain period of time before the procedure to avoid anesthesia complications. Ask your doctor about your situation.

What you can expect

Before the procedure

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

  • Radioactive solution. In this option, a weak radioactive solution is injected near the tumor. This solution is taken up by your 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. Your doctor might inject a harmless blue dye into the area near the tumor. Your lymphatic system delivers the dye to the sentinel nodes, staining them bright blue.

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

    The blue dye is typically injected just before the surgical procedure to remove the sentinel nodes.

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 under general anesthesia during the procedure.

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

If you've received radioactive solution before the procedure, the surgeon uses a small instrument called a gamma detector to determine where the radioactivity has accumulated and identify the sentinel nodes.

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

The surgeon then removes the sentinel nodes. In most cases, there are one to five sentinel nodes, and all are removed. The sentinel nodes are sent to a pathologist to examine under a microscope for signs of cancer.

In some cases, 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're moved to a recovery room where the health care team monitors you for complications from the procedure and anesthesia. If you don't have additional surgery, you'll be able to go home the same day.

How soon you can return to your regular activities will depend on your situation. Talk to your doctor.

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


If the sentinel nodes don't show cancer, you won't need other lymph node evaluation. If further treatment is needed, your doctor will use information from the sentinel node biopsy to develop your treatment plan.

If any of the sentinel nodes contain cancer, your doctor might recommend removing more lymph nodes to determine how many are affected.

In certain cases, a pathologist can examine the sentinel nodes during your procedure. If the sentinel lymph node shows cancer, you might need to have more lymph nodes removed right away rather than having another operation.

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