Vag et al. observed that the reported in vitro evidence of CXCR4 overexpression in malignancies such as pancreatic cancer, non-small cell lung cancer, prostate cancer, melanoma, breast cancer, hepatocellular carcinoma, glioblastoma, and sarcoma does not depict the in vivo distribution revealed by Pentixafor PET/CT [46]. The gene discussed is CXCR4; the disease is breast cancer.