PMC10090691_01
Morphologic and immunophenotypic evaluation of case1. Pathological examination showed architectural effacement by medium-sized tumor cells (A). The lymphoma cells have a pleomorphic morphology (B) and express CD20 (C), SOX11 (E), CD43 (F), MUM1 (G) and a high Ki67 proliferation index (H) while the lymphoma cells are negative for cyclin D1 expression (D). EBV-encoded RNA (EBER) was negative (I). A,E,F,G,Hx100; C,Dx200; B,Ix400.
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By immunohistochemistry (IHC),the tumor cells were positive for CD5, CD20, CD43, BCL6, MUM1,BCL2, MYC, and SOX11 and negative for cyclin D1, CD10, EBER, and LEF-1 ( Figure 1 ). Figure 1H ). Further, no IGH/CCND1 rearrangement was detected by using fluorescence in situ hybridization (FISH) analysis.
Identification of an IGKJ2::CCND3 fusion by DNA-targeted NGS. The formalin-fixed paraffin-embedded (FFPE) tissue in primary tumor tissues and plasma cell-free DNA (cfDNA) of pretreatment were detected by targeted DNA sequencing of 475 leukemia- and lymphoma-related genes. The Delly fusion calling tool was used to identify the number of chimeric reads (sequencing paired ends mapped to different genes) and split reads (spanning a fusion breakpoint) from the targeted DNA-seq data, and each SV was manually checked on the Integrative Genomics Viewer (IGV). The structure variations (SVs) profile showed a rearrangement between chromosome 2 and chromosome 6. The exact fusion breakpoints are localized at chr2: p11.2: 89,161,054 and chr6: p21.1: 41,915,909, respectively. Sequences supportive of IGKJ2::CCND3 fusion were detected by targeted DNA sequencing with a mutant allele frequency of 30.1% in tissue and 12.5% in plasma cfDNA (A). Schematic genome rearrangement of IGKJ2::CCND3 revealed that the exon 1-exon 5 remained completely intact, and two enhancers of chromosome 2 located upstream of CCND3, which may lead to a high expression of CCND3 protein (B).
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IGKJ2~CCND3 gene fusion was detectable in all samples ( Figures 2A, B ).