A protease-cleavable peptide linked to a fluorescent probe, with potential imaging activity. Upon intravenous infusion of the fluorescent protease-activated peptide AVB-620 before surgery, the peptide moiety of AVB-620 can be cleaved by proteases overexpressed by tumor cells. This activates the fluorescent probe and the tumor cells expressing the proteases can be detected using a fluorescence imaging system. This allows for the visualization and removal of the tumor during surgery.