PD-L1 FISH and PD-L1 IHC in a patient with response to pembrolizumab. (A) Representative PD-L1 FISH demonstrating a PD-L1 gene amplification in a patient with DLBCL. PD-L1 and centromere 9 FISH probes are shown in orange and blue, respectively. (B) Representative PD-L1 IHC demonstrating intense PD-L1 protein expression on tumor cells from the corresponding case in panel A.