ANALYSIS OF THE FREQUENCY OF MICROSATELLITE INSTABILITY AND P53 GENE MUTATION IN SPLENIC MARGINAL ZONE AND MALT LYMPHOMAS

Aims-Studies of the genetic characteristics of splenic marginal zone l ymphoma (SMZL) have failed to identify genetic changes specific to thi s tumour. Microsatellite instability is a type of genomic instability associated with different types of human cancer. Although microsatelli te instability is rare in B cell non-Hodgkin's lymphomas, it has been found in some specific subsets, such as marginal zone lymphomas arisin g in mucosa associated lymphoid tissue (MALT),where an association wit h p53 mutation has been described. Because it has been proposed that S MZL and MALT are close in histogenetic terms, this study investigated the comparative frequency of microsatellite instability and p53 mutati on in patients with SMZL and MALT lymphomas. Methods-Microsatellite in stability was investigated using seven microsatellite marker loci in 1 4 patients with SMZL and 20 patients with MALT lymphomas. In an attemp t to clarify the role of p53 gene mutation in the pathogenesis of SMZL , exons 5-8 were also investigated by polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) and direct sequencing in a total of 20 patients with SMZL and 22 patients with MALT lymphomas. Results-Microsatellite instability was not detected in patients with S MZL, although five of 20 patients with MALT lymphomas had microsatelli te instability. The frequency of p53 mutation was low in both series ( two of 20 patients with SMZL and one of 22 patients with MALT lymphoma s). No significant association was found between p53 mutation and micr osatellite instability. Conclusions These results indicate that micros atellite instability is not associated with the molecular pathogenesis of SMZL, confirming the relatively increased frequency of microsatell ite instability in MALT lymphomas, and perhaps suggesting that MALT an d SMZL have different mechanisms of tumorigenesis.