When comparing the tumor-to-background ratios of the xenografts, the ectopic HER2-positive tumors (tumor-to-blood ratio: 0.54 ± 0.08, tumor-to-muscle ratio: 13.13 ± 2.22) showed significantly higher ratios than the HER2-negative tumors (tumor-to-blood ratio: 0.10 ± 0.02, tumor-to-muscle ratio: 2.02 ± 0.09) at 4 h post-injection (p < 0.05); however, these differences began to decrease from 24 h onwards. This evidence concerns the gene ERBB2 and neoplasm.