In non‐follicular lymphoproliferative disorders, IGH/BCL2‐fusion is not restricted to chronic lymphocytic leukaemia

Summary The translocation t(14;18) and its t(2;18) and t(18,22) variants, which involve the BCL 2 genetic hallmark for follicular lymphoma ( FL ), have been reported in several cases of chronic B ‐cell lymphoproliferative disease ( CLPD ) and frequently in chronic lymphocytic leukaemia ( CLL ). We describe here the clinical, morphological, immunological, cytogenetic and molecular findings from 37 cases of t(14;18)‐positive CLPD , identified from our series of non‐ FL B‐cell neoplasms ( n = 993) that were routinely analysed in peripheral blood by conventional cytogenetics analyses. The FL diagnosis was excluded by morphology and immunology (the samples were CD 10 negative in all cases). The BCL 2 translocations were observed in 22 CLL cases, including 7 monoclonal B ‐cell lymphocytosis ( MBL ) cases re‐classified according to the new International Workshop on CLL criteria, six small lymphocytic lymphoma ( SLL ) cases, 1 splenic marginal zone lymphoma ( SMZL ) case and eight cases of unclassifiable CLPD with overlapping CLL / MZL features. In the CLL cases, the IGH / BCL 2 fusion was remarkably associated with trisomy 12 (13/22) and mutated IGHV status (20/21) and did not affect the outcome. Moreover, most of these CLL s harboured a low mutation load of BCL 6 gene and unmutated FAS ( CD 95 ) loci, which points to a post–germinal‐centre cellular origin.