[Extranodal marginal zone B-cell lymphoma of MALT-type]

[Gastric MALT-type lymphoma. Pathology, pathogenesis, diagnostics and therapy]

Helicobacter pylori infection plays a central role in the development of gastric MALT-type (mucosa-associated lymphoid tissue) lymphoma. Infection results in chronic H. pylori gastritis and stimulates together with antigens or autoantigens proliferation of B-lymphocytes which is the basis for the neoplastic transformation. Histology of MALT-type lymphoma is architecturally similar to the physiological MALT. Invasion and destruction of the gastric epithelium with development of so-called lympho-epithelial lesions is the most important diagnostic criterion. Cytologically MALT-lymphoma resembles centrocytes and monocytes. For definitive lymphoma diagnosis and for the differential diagnosis from other small cell lymphomas in the stomach immunohistochemistry can be helpful. The phenotype of MALT-type lymphoma is identical to non-neoplastic B-lymphocytes of the marginal zone (CD20+, CD5-, CD10- and CD23-). Individual therapy is strongly dependent from histological type and lymphoma stadium. Therapy modalities are H. pylori eradication, radiochemotherapy, surgery or a combination of these. Aim of the therapy is the complete lymphoma regression and cure of the disease.

[The spectrum of microbiological agents causing pulmonary MALT-type lymphomas. A 16S rRNA-based analysis of microbial diversity]

For several anatomical localisations of extranodal marginal zone B-cell lymphoma of MALT type (eMZBCL), an association with chronic inflammation caused by microbiological agents (e.g. Helicobacter pylori in the stomach) has been described. In the lung, a link between lymphomagenesis and a defined causative organism is still missing. A comprehensive diversity survey using 16S-rDNA library construction followed by restriction fragment length polymorphism (RFLP) analysis, sequencing, and phylogenetic tree construction was employed for nine cases each of BALT lymphoma and control lung tissues (normal foetal lung, pneumonitis, carcinoid). This highly sensitive method, hereafter termed SHARP screening allowed for identification of the entire bacterial population in the tissue in a cultivation-independent manner. It was noteworthy that in eight of the nine cases of BALT lymphoma, bacteria of the Alcaligenaceae family (Alcaligenes, Achromobacter, AKIW733), were detected, whereas none of the control cases showed the presence of these clades. 16S-rDNA library construction in combination with RFLP screening and phylogenetic analyses, hereafter described as SHARP screening, is a cultivation-independent tool for analysing the microbial environment in chronic inflammation processes giving rise to extranodal marginal zone B-cell lymphomas of MALT-type. Betaproteobacteria of the Alcaligenaceae family may be affiliated with and possibly involved in the lymphomagenesis of BALT lymphomas.