Schematic overview of potential mechanisms for the development of germinal center B cell-like and activated B cell-like diffuse large B cell lymphoma

Diffuse large B cell lymphoma (DLBCL) is a heterogeneous group of tumors derived from germinal center or post-germinal center B cells. Gene expression studies have divided DLBCL based on likely cell of origin. GCB-like tumors contain the (14;18) translocation (IgH/BCL-2 fusion gene) typical of follicular lymphoma and amplifications of the locus on chromosome 2 which codes for the c-Rel oncogene. ABC-like DLBCL is associated with loss of 6q21, trisomy 3, and gains of 3q and 18q21-22. This locus on 6q encodes the tumor suppressor gene PRDM1 (Blimp-1), which is a master regulator in the differentiation of mature B lymphocytes to plasma cells, loss of which may lead to inhibition of terminal differentiation. ABC DLBCL have high expression and constitutive activity of the nuclear factor kappa B (NF-KB) complex involved in the B cell receptor (BCR) signaling pathway. Type III DLBCLs have gene expression profiles that do not resemble either germinal center or post-germinal center B cells. The mechanism of its pathobiology is unknown.