PD-1 ligand amplification and overexpression in primary MLBCL. (A) qPCR-based DNA copy number analysis of PD-L1 in 41 primary MLBCLs. (B) RT-qPCR analysis of PD-L1 and PD-L2 transcript abundance in the same series of primary MLBCLs. Transcript abundance in tumors with normal or increased 9p24.1 is represented in box blots.