Translocations involving the short arm of chromosome 17 in chronic B-lymphoid disorders: frequent occurrence of dicentric rearrangements and possibleassociation with adverse outcome

Unbalanced translocations involving chromosome arm 17p, where the TP53 tumo r suppressor gene localizes, are rarely described in chronic lymphocytic le ukemia and small lymphocytic lymphoma (CLL/SLL), but recent use of molecula r cytogenetic techniques have indicated a significant incidence of TP53 del etions, suggesting the involvement of chromosome 17p in these disorders. By conventional karyotype, we have identified unbalanced translocations invol ving 17p in 14 out of 123 (11%) CLL/SLL patients with clonal abnormalities. Cases were characterized by resistance to chemotherapy and a poor clinical outcome. The karyotypes presented a high incidence of complex rearrangemen ts and 17p translocations were characterized by various partners. in 10 cas es a centric fusion was assessed by fluorescent in situ hybridization (FISH ) experiments using specific centromeric probes. The incidence of dicentric translocations in these series is therefore significantly higher than usua lly described, arising in up to 71% (10 out of 14 cases). In all cases, tra nslocations led to a monosomy 17p and to a TP53 monoallelic deletion. The a dverse clinical outcome confirms that structural abnormalities involving ch romosome 17p are associated with disease progression in patients with chron ic lymphoproliferative disorders.