Acquired gastric mucosa-associated lymphoid tissue (MALT): a review with special emphasis on association with extragastric diseases and management problems of gastric MALT.

Mucosa-associated lymphoid tissue is absent physiologically in normal gastric mucosa, but it can develop in some pathologies (dyspepsia, celiac disease, autoimmune diseases) due to certain (Helicobacter pylori, gluten) or uncertain (viruses?) antigenic stimuli. Its importance is related to the consideration that it is the background for the development of gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and its histologic progression to MALT lymphoma may be diagnosed using Isaacson's score. Monoclonal bands can be diagnosed in acquired gastric MALT as well as in gastric MALT lymphoma, but its role is unknown. To prevent development of MALT lymphoma from acquired MALT, currently anti-H. pylori treatment in all H. pylori- and MALT-positive patients is not suggested--only in patients with grade 3 of acquired MALT--due to the high risk of developing MALT lymphoma in these patients. At the same time, the etiology of gastric MALT in autoimmune extragastric diseases is not clear. Additional studies are needed to clarify this relation and its possible causes.