Imaging sentinel lymph nodes

As the technique of sentinel lymph node (SLN) biopsy has evolved over the last 22 years, it has become increasingly evident that accurate SLN imaging is vital to allow surgical removal of only the true SLN(s) and not other nodes. Identifying the lymphatic collectors draining a tumor site and following them to the draining SLNs defines which nodes need to be removed for careful histologic examination. Current technology allows the exact location of each SLN to be defined. This allows the full benefits of SLN biopsy to be achieved, that is, highly accurate lymph node staging with minimal morbidity. In melanoma and breast cancer, the current practice of preoperative lymphoscintigraphy (LS) using peritumoral injections of tracer or injection adjacent to an excision biopsy site with dynamic imaging to visualize the lymphatic collectors and delayed imaging including single-photon emission computed tomography/computed tomography gives the best results. This information informs the surgical approach and allows rapid excision of the SLNs at surgery.In patients with visceral tumors where the primary cancer site is difficult to access, it appears that using fluorophores that are fluorescent under near-infrared light, injected during surgery, is evolving as the preferred technique.