[Pathogenesis of MALT-type lymphoma].
Gastric marginal zone lymphoma, MALT-type (MZBCL) is thought to be derived from precursor lesions in follicular H. pylori-associated gastritis, that through accumulating genetic changes ultimately develop into an autonomously proliferating, monoclonal B-cell lymphoma. In the early phases of the disease, the proliferation is still at least partly dependent on the presence of H. pylori-induced T-cell help. Ongoing genetic alterations drive the process into an antigen independent phase. First of all, Fas mutations resulting in loss of function were found in a high frequency in MZBCL and gastric DLBCL and imply that Fas may act as a tumor suppressor gene. Therefore it is possible, that various Fas mutations may arise in mature B-cells during V(D)J recombination and other diversification processes in the course of immune responses as it was shown recently for the bcl-6 gene. Second, allelic imbalances suggest two different pathways of MZBCL development and progression. One group of tumors develops along the pathway determined by the dysregulation of the API2 and MALT1 genes brought about by the t(11;18). These tumors do not accumulate enough secondary genetic aberrations to transform into DLBCL and remain in the stage of MZBCL. Other MALT lymphomas characterized by the absence of the t(11;18) and increased accumulation of various clonal genetic aberrations, most frequently the 3q26.2-27 amplification, could be the source of tumors which eventually do transform into high-grade DLBCL.
Greiner
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Institut für Pathologie, Universität Würzburg.
D001363:Awards and Prizes; D002869:Chromosome Aberrations; D005858:Germany; D006801:Humans; D018442:Lymphoma, B-Cell, Marginal Zone / Q000235:genetics* / Q000473:pathology*; D010336:Pathology; D012955:Societies, Medical; D013274:Stomach Neoplasms / Q000473:pathology