Cytogenetic methods in chronic lymphocytic leukemia

In chronic lymphocytic leukemia of the B-lineage (B-CLL), cytogenetic alterations are highly relevant for prognosis and therapeutic decisions. With conventional techniques, chromosome banding analysis in CLL has been hampered by the low quality of metaphases and low rates of cytogenetic alterations due to a low in vitro proliferation rate of CLL cells. Thus, interphase fluorescence in situ hybridization (FISH) has become the standard technique for cytogenetic analysis in CLL. However, interphase FISH is not able to provide an overview on the whole karyotype. In order to improve chromosome banding analysis in CLL, specific stimulation techniques have been developed. These either use CD40 ligand or oligonucleotides (e.g., CpG) and IL-2 in combination. With the respective techniques, metaphase cultivation is successful in >90% of CLL cases and aberrant karyotypes can be detected in nearly 90% of CLL cases. This has allowed the detection of new clinically relevant subgroups (e.g., complex aberrant karyotype cases) and a more differentiated picture of distinct cytogenetic subtypes, e.g., cases with a 13q deletion. Efforts should continue to define the value of chromosomal banding in CLL focusing as well on the interaction with already established techniques such as interphase FISH or immunophenotyping.