[MALT-type non-Hodgkin's lymphoma: advances in biopsy diagnosis and pathogenesis]

Malignant Non-Hodgkin's lymphomas of the mucosa-associated lymphoid tissue display unique morphological and biological features. Unlike the situation in nodal lymphomas, they almost invariably arise from defined and recognisable precursor lesions, such as chronic infections or autoimmune diseases. From the diagnostic point of view, efforts have been undertaken to define (1) the minimal requirements for the unequivocal diagnosis of MALT-type lymphoma, (2) the regression stages after Helicobacter pylori eradication, and (3) to establish a grading system for the respective lesions. Of importance, it must be emphasized that in most cases the biopsy received in first-line is not enough in establishing a correct diagnosis with regard to biological and therapeutic implications. In particular, the accurate estimation of the biological aggressiveness of the tumour will in most cases require extensive rebiopsies. As in nodal tumours, the genetic constitution of low grade MALT-type lymphomas is more and more revealed. While data on the importance of numerical aberrations are conflicting, certain structural aberrations, such as the t(1;14) and the t(11;18), have been unequivocally linked to MALT-type lymphomas. Preliminary data suggest that these aberrations may target the apoptotic pathway. Their recognition may herald the evolution of new tumour features, such as independence from outer regulatory influences, obviously in early stages determined by the microenvironment and might be closely related to the site of tumour development and hence be a feature of the primary inflammatory disorder.