A 12q13 translocation involving the HMGI-C gene in richter transformation of a chronic lymphocytic leukemia

We report a case of Richter transformation of a chronic lymphocytic leukemi a with a 22q13 translocation involving the HMGI-C gene. Fluorescence in sit u hybridization analysis with the use of two different cosmid pools spannin g the entire HMGI-C region showed that the breakpoint on chromosome 12 was located in the HMGI-C gene, presumably within intron 3. In fact, the 3' reg ion of HMGI-C had been translocated to a derivative chromosome 6. This tran slocation was not visible at the cytogenetic level. Immunohistochemical ana lysis performed on the bone marrow smear demonstrated the expression of the HMGI-C protein specifically in the blasts, suggesting that the aberrant ex pression of the HMGI-C gene might have an important role in the process of leukemogenesis. (C) 2000 Elsevier Science Inc. All rights reserved.