This paper presents a novel concept involving sensing the back-reflected and absorbed light at two polarization states and at several wavelengths from gold nanorods (GNRs). While the GNRs are flowing in the bloodstream the reflected light has a high degree of polarization and only one resonance wavelength. When the GNRs are located in a tumor the reflected light has a low degree of polarization and two resonance wavelengths are detected. Such characteristics can assist in detecting a tumor in passive targeting and without labeling it.