Lymphoseek (technetium-99m-labeled diethylenetriamine pentaacetic acid-mannosyl-dextran, [Tc-99m]DTPA-mannosyl-dextran) is a radiotracer that accumulates in lymphatic tissue by binding to a mannose-binding protein that resides on the surface of dendritic cells and macrophages. Lymphoseek is a macromolecule consisting of multiple units of DTPA and mannose, each synthetically attached to a 10 kilodalton dextran backbone. The mannose acts as a substrate for the receptor, and the DTPA serves as a chelating agent for labeling with Tc-99m.