[Characterization of clonal B-cell populations in gastric MALT lymphomas and chronic gastritis by means of the polymerase chain reaction].

Amplification of the CDR3-region of the immunoglobulin (Ig) heavy chain gene rearrangement by means of the PCR yielded clonal products in the tumor DNA of 12 high or low grade gastric B-cell lymphomas of MALT-type. In four cases, additional clonal bands were found in different areas of tumor free mucosa diagnosed as chronic gastritis associated with Helicobacter pylori (HP). Most of these small clonal populations were found to share identical DNA sequences in their clone specific CDR3-regions with the main lymphoma in each patient; a finding consistent with the multifocal character of the disease. In two cases however, single clonal populations with different CDR3-regions revealed the existence of rare additional clonal B-cell-populations not related to the lymphoma and therefore possibly representing further independent foci.