Metastasis rather than primary tumors determines prognosis and mortality in the majority of cancer patients. Detection of metastatic lesions is critical to determine prognosis and suitable treatments. We developed a method for identifying sentinel lymph node (SLN) metastasis, using combined ultrasound and photoacoustic (US/PA) imaging augmented with glycol-chitosan-coated gold nanoparticles (GC-AuNP). Presence of metastasis affects accumulation of GC-AuNP in the SLN, which can be monitored via US/PA imaging (A).