Sentinel Lymph Node Biopsy: The Basics
What is the lymph system, a lymph node and a sentinel lymph node?
The lymph system is essentially the "housekeeping system" of the body. It is a network of vessels (tubes), which connect hundreds of lymph nodes located all over the body. These nodes can vary in size, but are normally up to about 2 centimeters in width. They contain cells that clear bacteria and other foreign debris from the body.
Lymph is a watery liquid that flows between cells in the body, picking up foreign debris and taking 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 ultimately 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 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), sometimes referred to as SLN biopsy, is a surgical procedure used to determine if there are cancer cells in the sentinel lymph node. During the procedure the surgeon identifies the sentinel lymph node(s), removes it and examines it to determine 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 removal of the primary tumor.
How is a sentinel lymph node biopsy performed?
A sentinel lymph node biopsy can be done in an outpatient setting or in the hospital. In some cases it is required that the patient stay overnight. General anesthesia is used. During the procedure the surgeon injects either a blue dye or a radioactive substance (in some cases both) near the tumor (or the area the tumor was removed from) in order to locate the position of the sentinel lymph node. The dye/radioactive substance will start to travel through the lymphatic system, allowing the surgeon to see which node(s) it goes to first. 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 identified and removed. Once located, the sentinel lymph node is removed. Once the sentinel lymph node is removed a pathologist will check for cancer cells. If cancer cells are found the surgeon may want to go back and remove more lymph nodes. The incision site is typically closed with sutures, often 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 allows the patient to avoid having all the lymph nodes in the area removed to check for cancer cells. Removing lymph nodes results in a risk of developing a complication called 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, 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 associated with having a sentinel lymph node biopsy performed. These risks can include pain and/or bruising at the surgical site, swelling, and infection. There is a risk of having an allergic reaction to the blue dye used during the procedure. The risk of lymphedema is significantly 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 assist with staging of cancer and avoid more extensive surgery that may not be necessary. 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.
Keidan RD et al. Medscape. Sentinel Lymph Node Biopsy in Patients with Melanoma. 2016. Found at: http://emedicine.medscape.com/article/854424-overview
Lyman 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.abstract
National 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