Studies of chromosomal copy number variation (CNV) have identified recurrent CNVs in PCNSL, and exome-sequencing analysis revealed that the CD79B, MYD88, TBL1XR1, and ODZ4 genes are most frequently mutated [14, 20, 21], in addition to PRDM1 and CARD11 [22, 23]. The gene discussed is MYD88; the disease is primary central nervous system lymphoma.