Variant t(14;18) in malignant lymphoma: a report of seven cases

The BCL2 gene was identified through molecular analysis of the breakpoints involved in the t(14;18)(q32;q21) found in the majority of follicular lymphomas (FL). Variant translocations leading to juxtaposing of the BCL2 with either the IGK or IGL gene have been recognized in B-cell malignant lymphoma, although they are rare. We identified seven lymphoma cases that had variant translocations. Three cases had simple translocations involving two chromosomal regions: t(18;22)(q21;q11.2) in two cases and t(2;18)(p11.2;q21) in the third case. Complex translocations affecting more than two chromosomes were seen in the remaining four cases. Fluorescence in situ hybridization using the LSI IGH/BCL2 DNA probes revealed rearrangements of the BCL2 gene locus in all cases. In addition, expression of BCL2 protein was seen in all cases; only five of the seven cases expressed BCL6 protein. Morphologically, the lymphomas were categorized as B-cell follicular lymphoma in six cases and in the seventh case as diffuse large cell lymphoma (Richter syndrome) transformed from preexisting chronic lymphocytic leukemia (CLL). In case 2, the variant t(18;22) was seen as a secondary aberration evolving from a trisomy 12 clone. The findings revealed that BCL2 rearrangements in some malignant lymphomas occur through variant simple or complex chromosomal translocations, but always involving the IGH, IGK, or IGL chromosomal site. In addition, fluorescence in situ hybridization proved to be an important tool in evaluating these cases by showing IGH/BCL2 gene fusion or repositioning of the BCL2 gene.