Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is a low-grade lymphoma comprising 7-8% of all B-cell non-Hodgkin lymphomas. Common sites of involvement include lung, head and neck, ocular adnexa, skin, thyroid and breast, but the gastrointestinal tract is by far the most common site and the stomach is involved in almost two-thirds of all cases. Infection and autoimmune diseases are commonly considered as etiopathogenetic factors, being related to chronic stimulation of B-cell proliferation. The association between Helicobacter pylori infection and gastric MALT lymphoma provides the best evidence of an etiopathogenetic link between lymphoma and infection. Indeed, successful eradication of this microorganism can be followed by lymphoma regression in most cases. In recent years the role of other pathogenetic factors including genetic predisposition, somatic genetic mutations and chemokines activity, has become more evident. Particularly specific genetic abnormalities have been observed in MALT lymphomas, with different distribution accordingly to the site of development.

This review, therefore, addresses the major findings obtained in the last few years about MALT lymphoma and summarizes recent advances in its molecular pathogenesis.