Oncoprint plot. Shown is the molecular analysis of the PTLs, PCNSLs, and DLBCLs (A) and PMBCLs (B). All tissue samples were obtained during standard diagnostic procedures. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue using anti-HLA class I (clone HC10, Nordic-MUbio), anti-HLA-DP,DQ,DR (clone CR3/43, DAKO), anti-PD-L1 (clone 22C3, DAKO), anti-PAX5 (clone SP43, Cell Marque), anti-CD10 (clone 56C6, ThermoFisher), anti-MUM1 (clone MUM1p, DAKO), anti-BCL2 (clone 124, Dako), and anti-BCL6 (clone PG-B6p, Dako) on a Labvision Autostainer 480S (ThermoFisher). Samples were scored positive for PD-L1 when membranous staining was observed in at least 5% of the malignant cells. Expression of EBV was determined by EBV-encoded RNA in-situ hybridization (EBER) probes (Biogenex). FISH for detection of BCL2, BCL6, and cMYC breaks was performed using probes and a FISH accessory kit (Dako). FISH for detection of PD-L1/2 CNAs was performed with the ZytoLight CD274/PDCD1LG2/CEN 9 Dual Color Probe (ZytoVision). FISH slides were evaluated in the context of serial sections stained for PD-L1 and B-cell markers (CD20 and PAX5) to localize tumor infiltrates. Samples were scored as having 9p24.1 disomy, polysomy, copy gain, or amplification. The presence of 3 or 4 green signals was classified as gain and the presence of 5 or more green signals was classified as amplification. Testing for somatic MYD88 and CD79B mutations was performed with allele-specific polymerase chain reaction, as described previously.⁷ Sanger sequencing was used to verify the presence of a mutation. (C) PD-L1 mRNA expression analysis of publicly available microarray data sets derived from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (accession numbers GSE10524, GSE61578, GSE34771 and GSE87371). All microarray data sets were generated with Affymetrix Human Genome U133 Plus 2.0 Array, and data analysis was performed with the R2: Genomics Analysis and Visualization Platform (http://r2.amc.nl). The horizontal line represents the median expression within each group. Differences among subtypes were tested by Kruskal-Wallis test with the post hoc Dunn’s test. *P < .05.