Gastric MALT-type lymphoma. Pathology, pathogenesis, diagnostics and therapy. Pathologe. 2010;31:188-194. [PMID: 20349062 DOI: 10.1007/s00292-009-1269-2]

[Plasma cell myeloma in the stomach?]

The detection of a diffuse infiltrate of heterogeneous small B-cells in the lamina propria mucosae invading the epithelium and destroying the glandular tissue by discrete aggregates of three or more marginal zone B-cells above the basal membrane (so-called lymphoepithelial lesions) is suspicious of a mucosa-associated lymphoid tissue (MALT) lymphoma of the stomach. The demonstration of a monoclonal B-cell population by immunohistochemistry, in situ hybridization or PCR excludes a benign lymphatic lesion. In the differential diagnosis with other small B-cell lymphomas in the stomach, a panel of five different immunohistochemical markers is useful to diagnose a small lymphocytic lymphoma (CD5 and CD23 positive), a mantle cell lymphoma (CD5 and cyclin D1 positive) or a follicular lymphoma (BCL2 and CD10 positive). The presence of the translocation t(11;18)(q21;q21) or the API2/MALT1 rearrangement could give further information about the clinical course and the prognosis of a gastric MALT lymphoma.

Role of Helicobacter pylori in gastric mucosa-associated lymphoid tissue lymphomas

Mucosa-associated lymphoid tissue (MALT) lymphoma is an indolent extranodal marginal zone B-cell lymphoma, originating in acquired MALT that is induced in mucosal barriers as part of a normal adaptive immune response to a chronic immunoinflammatory stimulus, most notably chronic infection by Helicobacter pylori (H. pylori). This antigenic stimulation initially leads to lymphoid hyperplasia; the acquisition of additional genetic aberrations culminates in the activation of intracellular survival pathways, with disease progression due to proliferation and resistance to apoptosis, and the emergence of a malignant clone. There are descriptions of MALT lymphomas affecting practically every organ and system, with a marked geographic variability partially attributable to the epidemiology of the underlying risk factors; nevertheless, the digestive system (and predominantly the stomach) is the most frequently involved location, reflecting the gastrointestinal tract’s unique characteristics of contact with foreign antigens, high mucosal permeability, large extension and intrinsic lymphoid system. While early-stage gastric MALT lymphoma can frequently regress after the therapeutic reversal of the chronic immune stimulus through antibiotic eradication of H. pylori infection, the presence of immortalizing genetic abnormalities, of advanced disease or of eradication-refractoriness requires a more aggressive approach which is, presently, not consensual. The fact that MALT lymphomas are rare neoplasms, with a worldwide incidence of 1-1.5 cases per 10⁵ population, per year, limits the ease of accrual of representative series of patients for robust clinical trials that could sustain informed evidence-based therapeutic decisions to optimize the quality of patient care.