Microsatellite instability analysis in typical and progressed mantle cell lymphoma and B-cell chronic lymphocytic leukemia

BACKGROUND AND OBJECTIVES: Microsatellite instability (MSI) is characterized by tumor-associated alterations in the germline size of microsatellite repeats caused by a reduced efficacy of the DNA mismatch repair machinery. The aim of this study was to investigate the presence of MSI in a number of cases of indolent and aggressive mantle cell lymphoma (MCL) and B-cell chronic lymphocytic leukemia (B-CLL) to determine its possible role in the initial development and progression of these disorders. DESIGN AND METHODS: We examined the presence of MSI in 28 B-CLL, 24 typical and 4 transformed B-CLL (Richter's syndrome) and 29 MCL, 19 typical and 10 blastoid variants by using a panel of 10 microsatellite markers and analyzed them using an AbiPrism 310 DNA sequencer. Fisher's exact test was used to compare categorical variables and Mann-Whitney's U-test for continuous variables. RESULTS: MSI alterations were not observed in any case of MCL or Richter's syndrome and in only three (13%) patients with typical B-CLL. Two of these patients also had loss of heterozygosity in one of the 10 sites examined. These patients presented with a more advanced stage, diffuse bone marrow involvement, and poorer performance status than patients without these alterations. INTERPRETATION AND CONCLUSIONS: These findings indicate that MSI is not involved in the pathogenesis or progression of B-CLL and MCL but may appear in a small subset of patients with advanced B-CLL.