Sentinel lymph node (SLN) biopsy and mapping
Sentinel lymph node (SLN) biopsy and mapping is a surgical procedure used primarily to assess the spread of cancer from a primary tumor to the lymphatic system. The SLN is defined as the first lymph node(s) that cancer is likely to reach, and determining whether these nodes contain cancer cells is crucial for staging the disease. The SLN mapping process involves the injection of a radioactive tracer and a blue dye near the tumor, which helps identify the sentinel nodes during surgery. Over recent years, alternative tracers like Indocyanine green fluorescence and magnetic tracers have been introduced, offering safer and more effective identification methods.
This procedure is commonly employed for breast cancer and melanoma, with research extending its application to other cancers, such as colon and head and neck cancers. After the SLNs are excised, they are examined for cancer cells, with results guiding further treatment decisions. While the procedure generally entails minimal hospitalization and recovery time, potential risks include pain, bruising, and, in rare cases, allergic reactions to the dye. Advances in imaging technologies are enhancing the accuracy of SLN identification, aiding in the effective staging of cancer and improving patient outcomes.
On this Page
Subject Terms
Sentinel lymph node (SLN) biopsy and mapping
DEFINITION: A sentinel lymph node (SLN) biopsy is a procedure in which the first lymph nodes to which cancer is likely to spread from the primary tumor are removed and examined to determine whether cancer cells are present. The process of identification of the SLNs is called SLN mapping.
Cancers diagnosed or treated: Mainly breast cancer and melanoma; SLN has been studied for use with other cancer types, such as colon and head and neck cancers
Why performed: Cancer cells spread first to one or several lymph nodes, called the sentinel lymph nodes (SLNs), before spreading to more distal lymph nodes and other sites in the body. Determining whether an SLN contains cancer cells provides the doctor with valuable information about whether the cancer has spread from its primary location.
Patient preparation: A small dose of a radioactive tracer compound and a blue dye are injected near the patient’s tumor several hours before surgery to allow these chemicals time to travel from the tumor region to any SLNs. In the mid-2020s, Indocyanine green fluorescence has come into use as it has proven to better identify cancerous cells. Additionally, magnetic tracers are also used for their increased efficiency and accuracy. These new tracers lack the dangers of the radioactive agents as well.
Steps of the procedure: Once the radioactive tracer compound and dye have reached the lymph nodes, the surgeon scans the area with a small Geiger counter and removes the radioactive lymph nodes through a small incision, using the presence of the blue dye for additional visual confirmation. A pathologist performs a preliminary examination of the nodes under a microscope. If cancerous cells are seen while the patient is still in surgery, additional lymph nodes may be removed at that time.
After the procedure: Pain or bruising at the biopsy site and temporary discoloration of urine or skin may occur. Some patients report postoperative nerve damage or swelling caused by lymph fluid accumulation in the area of the surgery. Rarely, a patient may be allergic to the blue dye used for sentinel node identification. Patients undergoing the procedure typically spend one day or less in the hospital.
Risks: A low percentage of SNL biopsies for breast cancer can turn out to be negative when other lymph nodes in the area do contain cancer.
Results: Doctors use SLN biopsy results to help determine the stage of cancer. A negative result implies that the cancer has not spread to the lymph nodes, and a positive result indicates that cancer is present in the SLN and, therefore, may be present in other lymph nodes. In this case, other lymph nodes may be removed from the area. Advances in imaging have enabled doctors to more easily identify the presence and severity of cancerous cells. Contrast-enhanced ultrasound using microbubble contrast agents allows doctors to identify cancerous cells and more accurately stage the cancer. Magnetic resonance imaging, combined with artificial intelligence, has also allowed doctors to more easily identify the extent of metastases, especially for breast cancer patients.
Bibliography
Chen, Steven, L., et al. “Lymphatic Mapping and Sentinel Node Analysis: Current Concepts and Applications.” CA: A Cancer Journal for Clinicians, vol. 56.5, 2006, pp. 292-309, quiz pp. 316-7, doi:10.3322/canjclin.56.5.292.
Cody, Hiram S. Sentinel Lymph Node Biopsy. Florence: Taylor, 2002.
Kennedy, Shania. “MRI-based Machine Learning Approach Predicts Breast Cancer Metastasis.” HealthITAnalytics, 31 May 2024, healthitanalytics.com/news/mri-based-machine-learning-approach-predicts-breast-cancer-metastasis. Accessed 26 June 2024.
Nelson, Bridget M. "Sentinel Lymph Node Biopsies in Cancers of the Skin, Colon, Head and Neck, and Breast." Proceedings (Baylor University. Medical Center), vol. 17, no. 2, 2004, pp. 99-103, doi.org/10.1080/08998280.2004.11927962. Accessed 26 June 2024.
Rocco, Nicola, et al. "New Techniques versus Standard Mapping for Sentinel Lymph Node Biopsy in Breast Cancer: A Systematic Review and Meta-analysis." Updates in Surgery, vol. 75, no. 6, 2023, pp. 1699-1710, doi.org/10.1007/s13304-023-01560-1. Accessed 26 June 2024.
Schauer, Alfred J., et al. The Sentinel Lymph Node Concept. New York: Springer, 2004.
“Sentinel Lymph Node Biopsy.” National Cancer Institute, 25 June 2019, www.cancer.gov/about-cancer/diagnosis-staging/staging/sentinel-node-biopsy-fact-sheet. Accessed 26 June 2024.
Subramonian, Subiksha, et al. "New Alternative Techniques for Sentinel Lymph Node Biopsy." Medicina, vol. 59, no. 12, 2023, p. 2077, doi.org/10.3390/medicina59122077. Accessed 26 June 2024.
Taghian, Alphonse G., and Michele Y. Halyard. Breast Cancer. New York: Demos, 2012.
Valsecchi, Matias, E., et al. “Lymphatic Mapping and Sentinel Lymph Node Biopsy in Patients with Melanoma: A Meta-analysis.” Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology, vol. 29.11, 2011, pp. 1479-87, doi:10.1200/JCO.2010.33.1884.