B2M and primary central nervous system lymphoma: In PMLBL, mutations in STAT6, SOCS1, TNFAIP3, and B2M and the frequency of 9p24 gain (including CD274 and PDCD1LG2) were significantly higher than those in DLBCL NOS, PCNSL, and PTL, which is also consistent with the results of previous studies.36