Elucidating a false-negative MYC break-apart fluorescence in situ hybridization probe study by next-generation sequencing in a patient with high-grade B-cell lymphoma with IGH/MYC and IGH/BCL2 rearrangements

The identification of MYC rearrangements in several mature B-cell neoplasms is critical for diagnostic and prognostic purposes. Commercially available fluorescence in situ hybridization (FISH) probe sets, including IGH/MYC dual-color dual-fusion (D-FISH) and MYC break-apart probes (BAPs), serve as the primary methodology utilized to detect MYC rearrangements. However, performing either IGH/MYC D-FISH or MYC BAP FISH studies in isolation has been reported to result in false-negative results because of the complex nature of 8q24 rearrangements involving the MYC gene region. We report a 60-yr-old male with newly diagnosed high-grade B-cell lymphoma with a negative MYC BAP study, but with positive BCL2 and BCL6 BAP studies. Per our current laboratory algorithm to concurrently interrogate the MYC gene region with both MYC BAP and IGH/MYC D-FISH probe sets, we performed IGH/MYC D-FISH studies and detected an IGH/MYC fusion. To further characterize the discrepant MYC results obtained by FISH, a next-generation sequencing strategy, mate-pair sequencing (MPseq), was performed and revealed a small insertion (∼200 kb) of the IGH locus downstream from the MYC gene that was undetectable by MYC BAP studies. This case highlights the importance of utilizing both IGH/MYC D-FISH and MYC BAP sets to detect potential cryptic MYC rearrangements and also demonstrates the power of MPseq to characterize complex structural rearrangements and copy-number abnormalities unappreciable by FISH.