Elucidating a false-negative break-apart fluorescence in situ hybridization probe study by next-generation sequencing in a patient with high-grade B-cell lymphoma with and rearrangements.

The identification of rearrangements in several mature B-cell neoplasms is critical for diagnostic and prognostic purposes. Commercially available fluorescence in situ hybridization (FISH) probe sets, including dual-color dual-fusion (D-FISH) and break-apart probes (BAPs), serve as the primary methodology utilized to detect rearrangements. However, performing either D-FISH or BAP FISH studies in isolation has been reported to result in false-negative results because of the complex nature of 8q24 rearrangements involving the gene region. We report a 60-yr-old male with newly diagnosed high-grade B-cell lymphoma with a negative BAP study, but with positive and BAP studies. Per our current laboratory algorithm to concurrently interrogate the gene region with both BAP and / D-FISH probe sets, we performed D-FISH studies and detected an fusion. To further characterize the discrepant results obtained by FISH, a next-generation sequencing strategy, mate-pair sequencing (MPseq), was performed and revealed a small insertion (∼200 kb) of the locus downstream from the gene that was undetectable by BAP studies. This case highlights the importance of utilizing both D-FISH and BAP sets to detect potential cryptic rearrangements and also demonstrates the power of MPseq to characterize complex structural rearrangements and copy-number abnormalities unappreciable by FISH.