Nodal marginal zone B-cell lymphomas may arise from different subsets of marginal zone B lymphocytes

Abstract

Nodal marginal zone B-cell lymphoma (MZL) is a rare and not extensively studied entity that accounts for approximately 2% of all non-Hodgkin lymphomas. Complementarity-determining regions 2 and 3 (CDR2, CDR3) of the immunoglobulin heavy-chain variable region (VH) genes were amplified by polymerase chain reaction (PCR), cloned, and sequenced in 8 patients with nodal MZL. All showed a potentially functional VH rearrangement. The use of VH gene families was unbiased and without overrepresentation of any particular VH gene or gene family. The presence of somatic VH mutations was detected, with a deviation from the closest germ line sequence ranging from 4% to 17% in 6 of 8 patients. In 3 mutations, the replacement-to-silent mutation ratio suggested the presence of an antigen-selected process. Sequencing different subclones of the same cloned PCR products allowed the detection of intraclonal variability in 4 analyzed patients. The observed pattern of VH 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 VH 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. © 2001 by The American Society of Hematology.