Chronic inflammation and extra-nodal marginal-zone lymphomas of MALT-type

Extranodal marginal zone lymphoma of mucosa associated lymphoid tissue (MALT) is an indolent B-cell non-Hodgkin lymphoma (NHL) arising in lymphoid populations that are induced by chronic inflammation in extra nodal sites. The stomach is the most commonly affected organ, and MALT lymphoma is clearly associated with a gastroduodenitis induced by a microbial pathogen, Helicobacter pylori, thus gastric MALT lymphoma represents a paradigm for evaluating inflammatory-associated lymphomagenesis. Variable levels of evidence have indicated a possible association between other microorganisms and non-gastric MALT lymphomas. In addition to infectious etiology, chronic inflammation arising as a result of autoimmune diseases such as Sjogren's syndrome or Hashimoto thyroiditis, poses a significant risk factor for developing NHL. Recently, genetic alterations affecting the NF-κB pathway, a major signaling pathway involved in many cancers, have been identified in MALT lymphoma. This review will present MALT lymphoma as an example of the close pathogenetic link between chronic microenvironmental inflammation and tumor development, showing how these observations can be integrated into daily clinical practice, also in terms of therapeutic implications, with particular focus on the NF-κB pathway.