The lymph node biopsy. A variety of methodologies play a role in the contemporary diagnosis of lymphoma. These include immunohistochemistry (IHC); flow cytometry (Flow); fluorescence in situ hybridization for genomic rearrangements (FISH); PCR for immunoglobulin and T-cell receptor gene rearrangements (PCR IG/TRG); PCR for targeted single cell mutations (eg, MYD88); high-throughput sequencing methods for analysis of RNA and DNA (RNAseq/NGS Methylation); and gene expression profiling (GEP). Karyotyping performed on metaphase spreads is still valuable in some settings.