FISH Analysis of IgH Rearrangement by 4 Kinds of Probes Involving IgH Genes in Multiple Myeloma: Improved Sensitivity for the Detection by Use of IGH Break-Apart Probe.

Background: IgH (immunoglobulin heavy chain) gene rearrangement is known to be the most frequent chromosome change in multiple myeloma. The detection of this genetic change is conveniently done by using fluorescence in situ hybridization (FISH) method recently. The aim of this study is to determine the utility of most commonly used probes, IGH/CCND1 dual color, dual fusion probe (Downers Grove, IL, USA), IGH/BCL2 dual color, dual fusion probe (Downers Grove, IL, USA), IGH/FGFR3 dual color, dual fusion probe (Downers Grove, IL, USA) and IGH dual color break apart rearrangement probe from Vysis Products (Downers Grove, IL, USA).

Methods: We applied four different probes of IgH FISH on 202 Korean patients with multiple myeloma for comparing the utility of four probes.

Results: 84 of 202 patients (41.6%) had the IgH gene rearrangement. 44 of 84 patients (52.4%) showed positive to all four probes, but 40 of 84 patients (47.6%) showed discrepancy. IGH dual color break apart rearrangement probe showed highly detectable rate (41.6%) compare to IGH/CCND1 (31.2%), IGH/BCL2 (27.7%) and IGH/FGFR3 (24.3%). Among patients who showed discrepancy between four probes, 20 of 40 patients (50.0%) were only positive to IGH dual color break apart rearrangement probe.

Conclusions: The IGH break-apart probe was qualitatively and quantitatively better than three other probes at initial diagnosis and during follow-up of myeloma. In conclusion, it would be most efficient and advisable to use the IGH break-apart probe at first, and then to identify the translocation partner in case of positive rearrangement of IgH.