A nanoparticle-based formulation containing carbon, with both a mean size of 150 nm, and potential use as a stain for lymph node draining. Upon injection of the carbon nanoparticles at the tumor site, these nanoparticles travel to regional lymph nodes and stain the lymph nodes black due to the presence of the carbon. This may allow for a more precise surgical removal of tumor-draining lymph nodes. Check for active clinical trialsusing this agent.