The higher in vivo tumor uptake of [99mTc]-HYNIC-cRDGfk-NPY resulted in higher overall tumor-to-muscle ratios, approximately 5.65 ± 0.94 and 7.78 ± 3.20, for MCF-7 and MDA-MB231, respectively, which should translate into images with higher contrast. The gene discussed is NPY; the disease is neoplasm.