What To Expect During a Sentinel Node Biopsy

Sentinel Node Biopsy
Sentinel Node Biopsy. Illustration @ A. D. A. M.

Sentinel Node Biopsy - An Important Diagnostic Test:

Sentinel node biopsy is a surgical diagnostic procedure done to remove a small sample of lymph nodes so they can be tested for metastasis. Those sentinel nodes will be examined to determine if cancer cells have metastasized (spread) beyond the original tumor. If done no other surgery is being done at the same time, this is an outpatient procedure, and is important in staging of your breast cancer.

If you are having a lumpectomy or mastectomy, sentinel node biopsy may be done along with that procedure. Here's what to expect during a sentinel node biopsy.

Getting Started With Medical Imaging:

Before this surgical procedure, your surgeon will need to know the locations of your tumor and the sentinel lymph node. A combination of imaging techniques will be used to find and mark these locations before surgery.

Finding The Tumor:

You will go to the Nuclear Medicine Department of the hospital or clinic where your sentinel node biopsy will be done. As you would for a mammogram or breast ultrasound, you will 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. The tumor site will be marked on your skin, so your surgeon can easily find it.

One Shot or Two – Blue Dye and Painkiller:

A radiologist or nuclear medicine specialist will inject a weak radioactive dye (technetium-labeled sulfur colloid), or a blue dye (isosulfan blue), or a combination of both, into the tumor site. This can be painful, so you may be given a choice of whether or not to have an injection of numbing medication first.

Since injecting the dyes can take longer than a flu shot usually does, you might like to seriously consider asking for the numbing medication, if it is not offered.

Lymph Node Mapping:

Once injected, the dyes need some time to travel from your tumor site to your lymph nodes. You will spend some time in a nearby waiting room, so bring along some reading material or music. When the dyes have reached their destination, you be asked to return to the Nuclear Medicine Department, and lie down on the exam table again. Imaging studies (lymphoscintigraphy) will be done to show which clump of lymph nodes is receiving the dyes, and that indicates where your sentinel lymph node will be found. The technician will mark this location on your skin, so your surgeon will know where to start looking.

Removing the Sentinel Lymph Node:

You will be brought into the operating room, where your surgeon will be ready to begin. You will be given general anesthesia. 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. 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.

Testing the Sentinel Node in Pathology:

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 will be done later.

Recovering From Your Sentinel Node Biopsy:

If blue dyes were used to find your sentinel lymph node, expect to see blue dye in your urine for about 24 hours. Sometimes there will be some bruising and blue dye on the skin around the incision. You will have a dressing and sutures to keep dry, and may need pain medications until healing begins. Use the surgery-side arm gently (no lifting!) for at least a week after the procedure. The stains from the blue dye will diminish and the bruises will heal, the incision itself will fade to a fine line over time.

Getting Your Biopsy Results:

Your surgeon or oncologist will call you about results of the biopsy as soon as the pathologist has completed their analysis. The report will include information on how many, if any, lymph nodes contain cancer cells. Ask for a copy of your pathology report and keep it with your health records. 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 the staging and treatment needed to treat your breast cancer.

Risks of Sentinel Node Biopsy:

A common result of a full lymph node dissection is a condition called lymphedema. Because lymph nodes in your armpit area are missing, the lymph fluid that is usually processed there can build up and cause swelling. If this persists or increases, it can become painful. However, if you require only a sentinel node biopsy, you will still have enough nodes to handle the lymph fluid that travels through your armpit region, so the rate of lymphedema in that case, is only about five percent.
False Positives or Negatives
Lymph nodes can vary in size, some small as a pinhead, others large as a bean. Your surgeon will be hunting through skin and fat, looking for blue-dyed nodes, and must use some skill and judgment. 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, and if the results are in any doubt, more nodes will be removed and tested, to make sure of accurate results.


National Cancer Institute. Sentinel Lymph Node Biopsy: Questions and Answers. Reviewed: 04/27/2005.

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