Many diffuse large B-cell lymphomas (DLBCLs) of the stomach are believed to represent high-grade transformation of low-grade marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type, which is of memory B-cell origin, displaying evidence for positive antigen selection and a low level of ongoing somatic mutation of the rearranged immunoglobulin heavy-chain variable region (V(H)) genes.
The observed pattern of V(H) mutations suggested that nodal MZL, formerly deemed a malignancy of memory B cells, may arise from different subsets of marginal zone B cells-the naive B cells that express unmutated V(H) genes-from memory B cells showing somatic mutations without intraclonal variation, and from germinal center B cells defined by their capacity to undergo the somatic hypermutation process.(Blood.2001;98:781-786)