NO EVIDENCE OF REPLICATION ERROR PHENOTYPE IN PRIMARY GASTRIC LYMPHOMA OF MUCOSA-ASSOCIATED LYMPHOID-TISSUE

Replication error (RER) phenotype, caused by deficiency of DNA mismatc h repair genes and revealed by widespread microsatellite instability, has been detected in subsets of a wide variety of solid tumors, but ra rely in lymphomas in general. So far, the involvement of RER phenotype in the pathogenesis of gastric lymphoma of mucosa-associated lymphoid tissue (MALT) type has not been conclusively established. We therefor e examined 9 microsatellite loci on 5 chromosomes [D2S123, D3S11, D3S1 261, D3S1262, D3S1265, D6S262, D18S59, a CTTT(T) repeat in intron 20 o f RBI gene and a CA repeat in p53 locus] in 33 cases of primary gastri c MALT lymphoma for evidence of microsatellite instability by polymera se chain reaction using primers end-labeled with [gamma-P-33] ATP. Alt hough novel-length allele was observed in 7 of 33 cases (21.2%), none of these 7 cases showed changes in more than one locus. RER phenotype was scored as positive in a case when more than I of the 9 examined mi crosatellite loci showed length alterations. Accordingly, none of the 33 cases had a RER phenotype. This result suggests that the pathogenes is of gastric MALT lymphoma does not involve RER phenotype. It is cons istent with the general observations in lymphomas, but is highly in co ntrast to a previous report showing more than 50% of MALT lymphomas wi th the RER phenotype. (C) 1998 Wiley-Liss, Inc.