dup(12)(q13-q22) and 13q14 deletion in a case of B-cell chronic lymphocytic leukemia

Cases with partial trisomy 12 have rarely been found in B-cell chronic lymp hocytic leukemia (CLL). We report our clinical, cytogenetic and fluorescenc e in situ hybridization (FISH) findings in a CLL patient with a duplication of part of the long arm of chromosome 12 between bands q13-q22. This patie nt was the only case with this duplication among the 112 cases (0.9%) of CL L cytogenetically analyzed in our laboratory. FISH studies using unique-seq uence specific probes for the RB-1 (retinoblastoma) gene and the D13S319 lo cus at the 13q14 band showed a monoallelic loss for the D13S319 locus (20% of cells) with a diploid RB-1 gene. Our case showed an atypical morphology (35% prolymphocytes), a high proliferation rate and progression of the dise ase, indicating that the duplication of this region may be equivalent to co mplete trisomy 12 in CLL patients. Copyright (C) 2001 S. Karger AG, Basel.