What Is a Sentinel Node Biopsy?

What to expect when undergoing this test

sentinel lymph node illustration
Illustration @ A. D. A. M.

Sentinel node biopsy is a surgical procedure doctors use to see whether early-stage breast cancer has spread beyond the tumor and into the lymphatic system. The sentinel nodes are the first lymph nodes a cancer is expected to move into. If there is evidence of malignancy there, there is a known possibility of it spreading to other parts of the body as the cancer cells circulate in lymphatic fluid.

It's often performed alongside surgery for breast cancer but may also be done on its own. It's also commonly used for melanoma and is being investigated for use in other cancers.

Purpose of Test

During a sentinel node biopsy, the surgeon removes a small sample of lymph nodes and sends it to a lab so it can be tested for breast cancer cells. In early-stage breast cancer, treatment recommendations depend on whether your lymph nodes are negative or positive for metastases (spreading cancer). Accurate staging will help you and your doctor choose the best options for you.

A second means of checking for cancer in the lymph nodes is axillary lymph node dissection. During this procedure, most of the lymph nodes in your armpit are removed and examined. This procedure may provide more evidence of whether cancer has spread.

Because sentinel node biopsy is less invasive, it's considered the standard of care when:

  • Early-stage breast cancer can be surgically removed
    AND
  • Axillary lymph nodes aren't enlarged

Breast Cancer Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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Risks and Contraindications

Sentinel node biopsy poses a 5% chance of lymphedema. This is the build-up of lymph fluid that is usually processed in the lymph nodes, which can cause swelling and, if persistent and progressive, pain.

While a concern, much of the reason behind doing a sentinel node biopsy instead of full lymph node dissection is to avoid lymphedema if possible; you will still have enough nodes to handle the lymph fluid that travels through your armpit region.

Contraindications

Some people with breast cancer are not considered candidates for this procedure. Your doctor may opt for axillary lymph node dissection instead of sentinel node biopsy when:

  • Your tumor is large or cancer has spread throughout your breast
  • You have inflammatory breast cancer
  • You have ductal carcinoma in situ (DCIS) and plan to have a lumpectomy
  • You're pregnant
  • Clinically positive axillary nodes are already confirmed
  • You've had metastases confirmed by fine-needle aspiration

Before the Test

Your surgeon or the facility where you're having the procedure should provide you with instructions.

Timing

The entire procedure takes several hours from the time you arrive until the time you leave. If you are also having breast cancer surgery the same day, expect it to take a significant amount of time.

Location

Sentinel node biopsy is performed in the nuclear medicine departments of hospitals and surgery centers. If the biopsy alone is being done, it will be an outpatient procedure. If you are having a lumpectomy or mastectomy, a sentinel node biopsy may be done at the same time as your breast surgery.

What to Wear

You'll need to wear a hospital gown for the procedure, so you may want to wear something that is easy to take off. For the trip home afterward, especially if you're having breast cancer surgery along with the biopsy, you'll want to have a soft but supportive bra, such as a sports bra, and a button-down shirt, since you'll need to avoid lifting your arms for a while.

Food and Drink

You'll need to fast for eight to 12 hours before surgery. Ask ahead of time about any medications that you can and can't take the morning of surgery.

Cost and Health Insurance

Check well ahead of time on the cost of your procedure(s) and how they'll be covered.

Check with your insurance company to see what charges you may face and when they'll be due. Make sure to ask whether your policy covers your surgeon, anesthesiologist, the facility, and the tests that will be run on your tumor after it's removed.

If you have a co-pay, expect to pay it before surgery unless the facility tells you otherwise.

What to Bring

When you arrive at the facility, make sure you have your:

  • Insurance card
  • Identification
  • A way to pay your co-pay, if necessary
  • Any papers your doctor may have given you
  • List of current medications
  • Medical history
  • List of allergies, including medication, latex, and adhesives

You may want to bring a book or electronic device to occupy your time before the procedure and while waiting for the dye to circulate. If you'll be staying overnight, you'll need things like a toothbrush, a change of clothes, and anything you want to make yourself more comfortable, such as a pillow or slippers.

During the Test

Be sure to arrive early enough before your procedure to get checked in and fill out any necessary paperwork. Throughout this appointment, you will interact with a variety of health professionals, including a nurse, a radiologist, and your surgeon.

Pre-Test

After you're called back, you'll be instructed to undress from the waist up and put on a hospital gown. Next, you will lie down on an exam table. A radiology technician will use an ultrasound machine to find your tumor and the tumor site will be marked on your skin, so your surgeon can find it easily.

A radiologist or nuclear medicine specialist will numb the area over your breast tumor. This may be done with a topical lidocaine patch (since this is a very tender area) followed by injection of lidocaine in your breast. When you are sufficiently numb, they will inject a weak radioactive dye (technetium-labeled sulfur colloid) and a blue dye (isosulfan blue) into the tumor site. This will help the surgeon identify your sentinel nodes.

The injection takes longer than a flu shot generally does and you may need several injections. It can become rather uncomfortable or painful.

Lymph Node Mapping

Once injected, the dyes need some time to travel from your tumor site to your lymph nodes. Once in the tumor site, the dyes must be picked up by the small lymphatic channels that travel to the lymph nodes.

While this is happening, you'll likely be in a nearby waiting room, where you can do something relaxing to pass the time.

When the dyes have reached their destination, you'll go back in and lie on the exam table again. Imaging studies (lymphoscintigraphy) will be done to show which clump of lymph nodes is receiving the dyes, and that points the way to your sentinel lymph nodes.

Throughout the Test

You'll be given a general anesthetic. Once you're asleep, the surgeon will use a hand-held probe to find the lymph nodes that contain the most radioactive dye.

In that location, your surgeon will make a small curved incision and look for the lymph nodes that have been stained with blue dye. Lymph nodes can vary in size, with some as small as a pinhead and others larger than a bean. Your surgeon will rely on skill and judgment as they hunt through skin and fat looking for dyed nodes.

Only one to three nodes will be removed unless many more are stained. These nodes are sent to the pathology department, where they are examined for metastasis and micrometastasis. Your incision will be closed and dressed, and you will be taken to recovery.

Post-Test

Once you're awake and alert, you'll either be moved to a hospital room (if you're staying overnight) or given follow-up instructions and discharged so you can go home.

After the Test

Once in the pathology lab, your nodes will be tested for cancer. Sometimes your surgeon will order a frozen section test for the nodes in order to get results right then. If your nodes do contain cancer cells, you may have a full lymph node dissection immediately to find the full extent of lymph node involvement. If a frozen section is not ordered and your nodes contain cancer, a full lymph node dissection may be done later.

Managing Side Effects

Most of the side effects of a sentinel node biopsy are relatively minor. Expect the blue dye used during the procedure to show up in your urine for about 24 hours. Sometimes there will be some bruising and blue dye on the skin around the incision as well, which will diminish.

You'll have a dressing and sutures to keep the incision dry and may need pain medications for a few days. Use your surgery-side arm gently for at least a week after the procedure; avoid lifting. The incision itself will fade to a fine line over time.

Interpreting Results

Your surgeon or oncologist will contact you about the results of the biopsy as soon as the pathologist has completed the analysis (which may be before you're discharged, if you're staying at a hospital). The report will include information on how many, if any, lymph nodes contain cancer cells.

If a node contains cancer, it is diagnosed as positive, and if no cancer is found in a node, it is diagnosed as negative. A diagnosis of positive lymph nodes means that your cancer has spread (metastasized) beyond the original tumor. These results will affect your staging and the treatment you need.

Metastases to lymph nodes do not mean a person has metastatic cancer. In fact, even early-stage breast cancers such as stage 1A can have micrometastases to lymph nodes. A positive sentinel node biopsy only means that your tumor has shown an "intent" to spread beyond the breast and lymph nodes.

Ask for a copy of your pathology report and keep it with your health records.

False Negatives

It's possible that the sentinel node will test negative (clear of cancer), but cancer may be in some other lymph nodes. This is called a false negative. To protect you from false results, your surgical and pathology teams will follow strict guidelines. If the results are in any doubt, more nodes will be removed and tested to make sure the diagnosis is correct.

Follow-Up

After your results are in, it's time to talk about what follow-up treatments you may need. Typically, after surgery, treatment options for those who test positive include:

A Word From Verywell

Having a sentinel node biopsy requires several steps and you may wonder why all of the efforts are needed. Choosing the best treatments for breast cancer requires accurate staging, and accurate staging requires knowing whether any cancer has spread to the lymph nodes.

In addition, determining if any lymph node involvement has micrometastases or macrometastases is crucial for making your future treatment decisions. The day of your biopsy may seem long, but the results will be significant in the days and months to come.

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