Molecular cytogenetic lesions in chronic lymphocytic leukemia

In the 90’s, only approximately 50% of chronic lymphocytic leukemia (CLL) could be shown to carry a chromosome defect, a figure reflecting inadequate cell division. The introduction of FISH allowed for the detection of chromosome aberrations in 80% of the cases and every patient could be included in a specific group according to a hierarchical cytogenetic classification as follows: 17p- > 11q- > +12 > 13q- > normal.1 In most studies, approximately 40% of CLLs were shown to carry isolated 13q-, 10-15% of the patients carried +12 or 11q-, 2-5% 17p- or 6q- or 14q32 translocations. The variable incidence of specific lesions in different phases of the disease reflects their correlation with biologic and clinical features (Table 1). Recently, the introduction of effective mitogenic stimulation by oligonucleotides and interleukin-2 (IL-2)2 showed that approximately 30% of CLL without chromosome defects by interphase FISH carried a chromosome lesion by CBA in regions not covered by the FISH panel of probes. Complex karyotypes could be documented in a substantial fraction of cases in association with unfavorable prognostic factors and inferior clinical outcome.2