A synthetic visual lymphatic imaging agent. Injected into the periphery of the tumor site, isosulfan blue localizes to the lymphatic system and aids in the surgical identification of tumor sentinel nodes which stain blue. orA dye made in the laboratory that helps identify the sentinel lymph node (the first lymph node that cancer spreads to from a primary tumor). Isosulfan blue is injected at the edge of a tumor and travels through the lymph fluid to lymph nodes near the tumor. The sentinel lymph node is identified by removing lymph nodes that are stained with the blue dye and looking for cancer cells under a microscope.