Lymphoscintigraphy

Lymphoscintigraphy is a nuclear medicine imaging study for mapping the lymphatic system with scintigraphy. Attempts at understanding and mapping the lymphatic system began in the 1600s with the discovery of the cisterna chyli and thoracic duct. The lymphatic drainage of the breast was first described in 1786 and identified 2 dominant drainage pathways of the breast: the axillary lymphatic basin and the internal mammary nodes. Subsequently, intradermal or parenchymal injection of scintigraphic agents was found to be equivalent to an intralymphatic injection. In the late 20th century, protocols employing radiopaque contrast agents to visualize the first lymph node to receive the contrast agent, also termed the “sentinel lymph node,” were developed. Several radioisotopes have been used for lymphoscintigraphy; current lymphoscintigraphic techniques utilize Technetium Tc 99m sulfur colloid. The ideal radiotracer for lymphoscintigraphy will demonstrate rapid transfer to and prolonged stay within the lymph node. Understanding the map of lymphatic drainage patterns of anatomical structures defines the clinical application of lymphoscintigraphy. A sentinel lymph node is the first node that accepts lymphatic drainage from an anatomical site. In cases of malignancy, such as malignant melanoma or breast cancer, the sentinel lymph node is most likely to harbor occult metastases. Sentinel lymph node histopathologic analysis, in the absence of overt metastases, can potentially preclude the need for adjuvant therapies, including lymphadenectomy, radiotherapy, chemotherapy, or more invasive surgical procedures. Lymphoscintigraphy has become the standard of care when managing select breast cancer and melanoma cases; other applications include the evaluation of lymphedema.