We evaluated basophils from patients who had been previously treated with targeted anti-cancer therapies: (i) the anti-VEGF mAb bevacizumab [47,48,49] (n = 9), the only antibody approved for the treatment of ovarian cancer, and the administration of which has been reported to trigger hypersensitivity [48,49,50]; (ii) the poly-ADP ribose polymerase (PARP) inhibitors olaparib (n = 1) and niraparib [51,52,53] (n = 1); (iii) the anti-PD-L1 mAb avelumab [47] (n = 2). This evidence concerns the gene CD274 and cancer.