Sentinel Node Biopsy
J. Taylor Whaley, MD
Last Modified: June 14, 2012
What is a sentinel node biopsy?
- A sentinel node biopsy, or sentinel lymph node dissection, is a procedure that is performed to look for cancer in the nearby draining lymph nodes after a cancer is diagnosed. When a cancer is discovered, it is very important for your medical team to know how aggressive the tumor is and if the tumor has spread beyond its original location. The first place most cancers spread to is the surrounding lymph nodes. The purpose of the procedure is to obtain a tissue sample of the nearest lymph nodes to help with the staging of the cancer.
- There are thousands of lymph nodes found throughout the body, in nearly every organ. They serve the very important role in the immune system of filtering circulating fluids as well as housing white blood cells that help fight infections. When tumor or cancer cells develop the ability to spread to lymph nodes, the initial site of spread is referred to as the sentinel lymph node. When lymph nodes are involved with cancer, they are frequently enlarged, painless, and hard.
- Sentinel lymph nodes biopsies are most frequently performed in breast cancer, melanoma, and other skin cancers. Its role in other types of cancers is being investigated. Sentinel node biopsies have been used for the past 10-20 years, most frequently in breast cancer. They have replaced the axillary dissection procedure, which removed most of the nodes in the underarm; however, if the sentinel node is involved with cancer, a full dissection will frequently be performed.
- Sentinel node biopsies are outpatient surgeries, well tolerated with few complications, and widely available throughout most developed countries.
How is this test performed?
- A sentinel node biopsy is performed by a surgeon to evaluate the extent of spread of a newly diagnosed cancer. Frequently, the sentinel node dissection will be performed with the lumpectomy, mastectomy, or surgical resection of the tumor. If the sentinel node biopsy is performed alone, it may occur under just local anesthesia.
- To perform a sentinel lymph node biopsy, the surgeon will inject the area near the tumor with a very small amount of a radioactive tracer or a blue dye. The substance injected is based on the surgeon’s preference. If radiotracer is used, the amount of radiation is very low, even less than that of an X-ray. The substance is injected just below the skin near the tumor. For breast cancer, it can also be injected near the areola. The injection generally occurs anytime from 30 minutes to several hours before the dissection. Because all fluid that surrounds the area is drained to lymph nodes, the sentinel node will become evident.
- At the time of the dissection, the surgeon will make a small incision after numbing the area. Using a Geiger counter, which is a small device that is very sensitive to low doses of radiation, the surgeon can locate the lymph node or nodes that drain the area near the tumor. If the blue dye is used, the lymph node will appear blue. The surgeon will then carefully resect, or remove, the lymph node or nodes.
- After the tissue is collected, the sample is placed onto a glass slide for a pathologist to study and evaluate. A pathologist is a type of doctor that specializes in looking at tissues under the microscope. After the pathologist has established a diagnosis, a report will be generated for your doctor.
- A sentinel lymph node dissection generally takes 45-60 minutes to perform. If a tumor resection will happen at the same time, the procedure will be longer, based on the removal of the tumor.
- Similar to any surgical procedure, the most important risk associated with a sentinel lymph biopsy is bleeding. Generally, there is very little bleeding associated with the procedure, although rarely, a hematoma, or a pocket of blood, will collect at the site of the biopsy. A collection of fluid, known as a seroma, can also occur after the dissection. This area can be tender and slightly uncomfortable but should resolve within a few weeks. If there is severe pain following the procedure, you should contact your doctor immediately. A sentinel lymph node dissection also has very low risk of lymphedema. Lymphedema is swelling in the arm after lymph nodes are removed. This can occur because the normal draining pattern is disrupted.
- Additionally, there is always a risk of infection and you should call your doctor if you develop fevers or if the area becomes inflamed.
How do I prepare for a sentinel lymph node biopsy?
- There is minimal preparation for a sentinel lymph node biopsy.
- If general anesthesia will be used, you will need to fast prior to the procedure. If local anesthesia will be used, no preparation is needed; however, if you are on blood thinners, your doctor will likely have you stop them several days in advance. You should also stop taking aspirin, some anti-inflammatory medications, and any supplements that may increase the risk of bleeding. These details should be discussed when the biopsy is scheduled.
How do I interpret the results of a pathology report?
- Following the biopsy, the tissue sample is processed by a pathologist. A preliminary report may be given to the doctor using a frozen sample of the tissue; however, the final report generally takes several days. The pathologist then generates a report for your doctor.
- The report generally states the patient’s name, date of birth, site of biopsy, and indication (reason for the test) at the top of the report. Pathology reports follow a standard outline regardless where they are obtained. The findings are discussed in a very systematic approach. For this reason, it is very important to discuss the results with your doctor.
- The first paragraph typically reports the final diagnosis. This is a summary of the findings, often generated to answer the question posed by the ordering physician. The report will commonly state the findings are benign (not cancer), malignant (cancer), or unable to be determined.
- The following paragraphs of the report generally include the specific technical information involved in obtaining and processing of the sample. The details of the diagnosis can also be found here. Because reports are generated for other medical professionals, the terminology is often medically oriented and can be difficult to interpret.