Characterization of IGH rearrangements in non-Hodgkin's B-cell lymphomas by fluorescence in situ hybridization.

Rearrangements involving the IGH gene have been identified in about 50% of non-Hodgkin's B-cell lymphomas (NHL) and correlated to clinical relevant subgroups. However, the detection rate varied greatly with the technique used. The incidence of IGH rearrangements was analyzed using several fluorescence in situ hybridization (FISH) techniques on metaphases obtained from 57 patients with nodal NHL. An IGH rearrangement was identified in 42 cases (73.7%). A t(14;18)(q32;q21) was found in 17 of the 20 follicular lymphomas (85%) studied and a t(11;14)(q13;q32) in 10 of the 11 mantle cell lymphomas (91%). IGH rearrangements were identified in 12 of the 26 diffuse large B-cell lymphomas (46%), including 5 t(14;18)(q32;q21) and 2 t(3;14)(q27;q32). Conventional cytogenetics was uninformative in several cases. However, the complemented analysis using Multi-FISH and/or chromosomal whole paint enabled the characterization of complex IGH translocations in follicular lymphomas and mantle cell lymphomas and the identification of all the chromosomal partners involved in the IGH rearrangement in diffuse large B-cell lymphomas. This study shows the interest of using metaphase FISH in addition to conventional cytogenetics. Following banding techniques, FISH with the IGH dual color probe could be the first approach in NHL, after which chromosome painting and M-FISH could be used to identify the chromosomal partner involved in the IGH rearrangement.