MUTATOR PHENOTYPE IN A SUBSET OF CHRONIC LYMPHOCYTIC-LEUKEMIA

The replication error phenotype (RER(+)), characterized by widespread microsatellite instability, is an important feature of tumors from pat ients with hereditary nonpolyposis colorectal carcinoma (HNPCC). This widespread instability affects repeat tracts of all lengths and is usu ally attributed to mutations of critical mismatch repair genes. Recent ly, several reports described occasional microsatellite alterations in tumors not associated with HNPCC. However, a true mutator phenotype ( RER(+)) is very rare outside of HNPCC-associated malignancies. We exam ined 29 cases of chronic lymphocytic leukemia (CLL), the most common l eukemia in the Western world for evidence of microsatellite instabilit y, We identified a mutator phenotype in (2/29) 7% of the cases studied , These data suggest that the mismatch repair pathway may be altered i n at least a subset of patients with CLL. (C) 1996 by The American Soc iety of Hematology.