Four novel non-random chromosome rearrangements in B-cell chronic lymphocytic leukaemia: 6p24-25 and 12p12-13 translocations, 4q21 anomalies and monosomy 21

Nine patients with previously unreported chromosome changes were identified among 209 B-cell chronic lymphocytic leukaemia (CLL) cases: three patients had a translocation involving 6p24-25; three had a 12p12-13 translocation; two had 4q21 involvement (one with coexisting 6p anomaly); and two had monosomy 21. Interphase fluorescence in situ hybridization (FISH) detected some cryptic aberrations (+12, 6q-, 17p-, 11q-) in those patients with 6p translocations, whereas only a cytogenetically undetected 13q14 deletion was found in the remaining cases. Atypical morphology was noted in six cases, including both cases with monosomy 21, two cases with 6p and 4q21 anomaly and one case with 12p involvement. Four of these cases also had more than one phenotype deviation with respect to the classical CLL phenotype. Disease progression after 21-51 months (median 41) was noted in two cases with 6p and 4q21 involvement and in one case with 12p anomaly and monosomy 21. We arrived at the following conclusions: (i) 6p24-25 and, possibly, 4q21 lesions represent non-random events in CLL, occurring in association with other well-known unbalanced rearrangements; (ii) 12p rearrangements and monosomy 21 may possibly represent early chromosome defects that are not associated with the classical DNA gains and losses known to be present in the majority of CLL; and (iii) atypical morphology and immunophenotype as well as disease progression were frequently observed in these cases