Chromosome Abnormalities In

With proper mitogen stimulation in vitro in dedicated laboratories, most CLL samples present mitotic cells, and clonal chromosome abnormalities are found in about one-half of the cases studied (5,6). In more than one-half of cases with clonal abnormalities, there is only one single chromosome aberration, and in one-fourth of those with clonal abnormalities there are complex

From: Contemporary Hematology Chronic Lymphocytic Leukemia: Molecular Genetics, Biology, Diagnosis, and Management Edited by: G. B. Faguet © Humana Press Inc., Totowa, NJ 163

Fig. 1. Chromosomes involved in the most common clonal abnormalities in CLL, divided into single abnormalities and complex (here, two or more) abnormalities. Data are from the International Working Party on Chromosomes in CLL, for 662 CLL patients (6).
Fig. 2. Balanced clonal chromosomal abnormalities in CLL. All translocations reported in at least four CLL-patients in the Mitelman Database of Chromosome Abnormalities in Cancer 2001 (26).

karyotypes with three or more clonal cytogenetic events. Subclones, i.e., cells with some but not all the clonal abnormalities of a certain population, are commonly found.

The pattern of chromosomal abnormalities in CLL is quite different from that of most other leukemias and lymphoproliferative disorders. In CLL, specific balanced translocations are distinctly rare, whereas trisomies (mainly +12) and deletions (mainly involving 13q, 11q, and 6q) are common (Fig. 1). The most common translocation is the t(11;14) (Fig. 2), which is the characteristic finding of mantle cell lymphoma.

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