Sentinel Lymph Node Biopsy: The Basics

Author: OncoLink Team
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What is the lymph system, a lymph node, and a sentinel lymph node?

The lymph system is the "housekeeping system" of the body. It is a network of vessels (tubes), that connect hundreds of lymph nodes found all over the body. These nodes can vary in size but are normally up to about 2 centimeters wide. They contain cells that help clear out bacteria and other foreign debris from the body.Lymph is a watery liquid that flows between cells in the body. This liquid picks up foreign debris and takes it into the lymph node for filtering. From the lymph node, the debris may pass through several more nodes in the system before being dumped into the bloodstream to be cleared by the liver. The lymph system flows throughout the body, and also includes the spleen and thymus gland. Cancer cells can spread to other parts of the body through the lymphatic system. Because of this, lymph nodes are one of the earliest sites of spread (metastasis) for some cancers. A sentinel lymph node(s) is the lymph node(s) that cancer cells are most likely to spread to first from a primary tumor.

What is a sentinel lymph node biopsy?

A sentinel lymph node biopsy (SLB), also called an SLN biopsy, is a surgical procedure used to see if there are cancer cells in the sentinel lymph node. During the procedure, the surgeon identifies the sentinel lymph node(s), removes it, and tests it to see if cancer cells are present in the node. The biopsy is often done during the surgery to remove the primary tumor but can be done in a separate procedure, either before or after the removal of the primary tumor.

How is a sentinel lymph node biopsy done?

A sentinel lymph node biopsy can be done in an outpatient setting or in the hospital. In some cases, you will stay overnight in the hospital. You will have either a blue dye or a radioactive substance (in some cases both) injected near the tumor or in the area where the tumor was removed from. This part of the procedure can be done in the nuclear medicine department a few hours before the biopsy or can be done in the operating room. The dye/radioactive substance is used to find the sentinel node. The dye/radioactive substance travels through the lymphatic system. The surgeon can see which lymph node(s) it goes to first - this is the sentinel node.General anesthesia is used to help you sleep before the biopsy procedure. The surgeon uses a tool that can detect the radioactivity, or looks for the dye, to find the sentinel lymph node. There may be more than one node found and removed. Once found, the sentinel lymph node is removed. Once the sentinel lymph node is removed, a pathologist will check for cancer cells under a microscope. If cancer cells are found, the surgeon may want to go back and remove more lymph nodes. The incision site (cut in the skin) is closed with dissolvable sutures that will be absorbed by your body. The incision will then be covered by a bandage.

What is the benefit of removing only the sentinel node(s)?

Sentinel node biopsy avoids having all the lymph nodes in the area removed to check for cancer cells. Removing lymph nodes leads to a risk of developing lymphedema, where the lymph fluid is unable to drain from the area (most often an arm, leg, or the head/neck). This can result in swelling that can be painful, causing difficulty using or moving that limb, and an increased risk of serious infection in that limb.

What are the risks associated with sentinel lymph node biopsy?

There are some risks and possible side effects of having a sentinel lymph node biopsy. These risks can include:
  • Pain and/or bruising at the surgical site.
  • A small collection of fluid under the incision (seroma).
  • Swelling.
  • Infection. 
  • There is a risk of having an allergic reaction to the blue dye used during the procedure. 
  • The risk of lymphedema is much lower with SLB, but it is not zero. If you develop any swelling in the arm or leg where the SLB was performed, notify your provider right away.
The use of sentinel lymph node biopsy can help with the staging of cancer and avoid more extensive surgery that may not be needed. The more lymph nodes that are removed, the greater the risk of other, more serious side effects such as lymphedema, seroma, numbness and tingling at the surgical site, and losing the ability to move the affected body part. This procedure is most often used in breast cancer and melanoma but is being studied in other cancers.To learn more about the procedure and what to expect, read Surgical Procedures: Sentinel Lymph Node Biopsy.

References

Keidan RD et al. Medscape. Sentinel Lymph Node Biopsy in Patients with Melanoma. 2016. Found at: http://emedicine.medscape.com/article/854424-overviewLyman GH et al. Sentinel Lymph Node Biopsy for Patients with Early-Stage Breast Cancer: American Society of Clinical Oncology Clinical Practice Guideline Update. Journal Of Clinical Oncology. 2014. Found at: http://jco.ascopubs.org/content/early/2014/03/18/JCO.2013.54.1177.abstractNational Institute of Health. National Cancer Institute. Sentinel Lymph Node Biopsy. 2011. Found at: http://www.cancer.gov/about-cancer/diagnosis-staging/staging/sentinel-node-biopsy-fact-sheet

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