B2M and diffuse large B-cell lymphoma: The A53 subtype is enriched of ABC DLBCL and is characterized by TP53 mutations and deletions, with extensive aneuploidy, plus deletions of the B2M locus, amplifications of CNPY3 (6p21), 6q losses (TNFAIP3 and PRDM1), gain/amplification of 3q (NFKBIZ) and BCL2 amplifications.