Optical Genome Mapping Is a Powerful Diagnostic Tool in Non-Hodgkin Lymphoma

Abstract

Non-Hodgkin lymphoma (NHL) is a diverse and heterogeneous group of hematological malignancies. These lymphomas arise from the clonal proliferation of either B/T or natural killer lymphocytes, and their correct classification relies partly on identifying characteristic structural variants and copy number alterations. Current standard-of-care technologies for detecting these genomic features, chromosome banding analysis (CBA) and fluorescent in situ hybridization (FISH), are labor intensive and have specific limitations. CBA has low resolution and relies on viable cell culture, whereas the targeted approach of FISH does not provide the whole genome view required for comprehensive disease characterization. This highlights the need for higher–resolution nontargeted genomic methods. Previous studies have evaluated optical genome mapping (OGM) as a whole genome alternative for cytogenomic characterization in NHL diagnostics but were restricted in number and to cases with peripheral blood and/or bone marrow invasion. Here, we selected a comprehensive cohort of 110 NHL cases (79 B-NHL and 31 T-NHL/natural killer-NHL) derived from different types of tissue biopsies, all with established histopathological diagnoses. Seventy-eight samples were genomically well characterized at diagnosis by CBA and FISH. The remaining 32 cases were included because of previous CBA failure, although FISH data were available for 20 cases. OGM provided informative results in 94% of the cohort, with a high concordance rate of 97.6% compared with CBA/FISH in detecting clinically relevant aberrations. The 2 variants that were missed were both present at the detection threshold of OGM. In contrast, OGM successfully resolved 26 samples with previous CBA failure and detected 3 additional disease-defining events, resulting in diagnostic reclassification of 1 patient. Finally, OGM identified novel recurrent aberrations that warrant further investigation into their pathogenetic implications. To conclude, OGM robustly detects clinically relevant structural variants and copy number alterations and presents a promising alternative to CBA and FISH in routine diagnostic evaluation of NHL.