Based on the identification of the first highly potent, synthetic CXCR4-targeted anti-HIV antagonists in the late 1990s [89,90], and fueled by the recognition of the important role of CXCR4 in cancer growth, progression and metastasis in the early 2000s [91], the development of CXCR4-targeted imaging agents has been a field of highly active research since the mid-2000s (Figure 2). This evidence concerns the gene CXCR4 and cancer.