Sentinel lymph node (SLN) (SLN)

A sentinel lymph node (SLN) is defined as the first lymph node or group of nodes to which cancer cells are most likely to spread from a primary tumor (StatPearls, 2023). In clinical oncology, the sentinel lymph node biopsy (SLNB) is a standard diagnostic procedure used to determine the extent of cancer spread, particularly in breast cancer and melanoma (National Cancer Institute, 2021). The procedure involves injecting a tracer—such as a radioactive isotope or a blue dye—near the tumor, which then travels through the lymphatic system to the sentinel node (PubMed, PMID: 30085234). If the sentinel node is free of cancer, it is highly probable that other downstream lymph nodes are also clear, potentially sparing the patient from more invasive axillary or regional lymph node dissections (American Cancer Society, 2022). While not a therapeutic target itself, the sentinel lymph node is a critical anatomical site for staging and guiding treatment decisions. Various diagnostic agents are designed to localize within these nodes by exploiting lymphatic flow or specific cellular receptors like CD206 on resident macrophages (FDA, Lymphoseek Label).

Other names

Sentinel nodeFirst-draining lymph node

Diagnostic tracers are sequestered in the sentinel lymph node via passive lymphatic flow or active receptor binding (e.g., tilmanocept binding to CD206 on macrophages) to allow for visual or radioactive identification during surgery (FDA, 2013; PubMed, PMID: 23514000).