Deletions of Chromosome

The long arm of chromosome 11 is also frequently deleted in CLL (Fig. 3), sometimes as terminal deletions with variable breakpoints (Fig. 4), but also as interstitial deletions (6), without

Fig. 4. Unbalanced clonal chromosomal abnormalities in CLL according to specific band. All breakpoints reported in at least 10 CLL patients in the Mitelman Database of Chromosome Abnormalities in Cancer 2001 (26).

a clear-cut minimally deleted region. The only commonly recurring translocation in CLL involves the cyclin D1/BCL-1 gene on 11q13, which by translocation is juxtaposed to the immunoglobulin heavy chain genes on chromosome 14 band q32. This abnormality is more typically found in mantle cell lymphoma than in CLL, but there are phenotypically well-defined CLLs reported to have this translocation, indicating a relationship between these two CD5+ chronic B-cell malignancies. Chromosome 11 abnormalities rarely occur as single abnormalities (Fig. 1), and, thus, in the so-called hierarchical model of chromosomal abnormalities in CLL proposed by Dohner et al. (10), the designation 11q deletion is likely to be a surrogate marker for a complex karyotype.

Deletions of 11q have been found in younger patients with more aggressive disease and more lymphadenopathy (20), whereas the prognostic impact was not seen among the older population that constitutes most CLL patients.

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