PMC9752035_01
(A-E) Preoperative MR imaging and intraoperative stills. T2-weighted MRI revealed an inhomogeneous hyperintense lesion in the left frontal lobe (A). T1-weighted MRI showed a hypointensity of the lesion (B). Enhanced T1-weighted MR images indicated no enhancement of the mass, with a vessel (red arrow) underneath the tumor (C, D). The intraoperative stills revealed the tumor was regionally confined in a lobe. The dotted blue line in the panel delineated the region of the tumor. The red arrowheads indicate left frontal bone deformation and thinning caused by long-term tumor compression(E). (F-N) Histopathology and immunohistochemistry staining of the Formalin-fixed paraffin-embedded (FFPE) tissue tumor tissue sections. H&E staining revealed numerous round monotonous oligodendrocyte-like cells, with neurons floating in the matrix. The multinodular glial architecture was also observed (inserted) (F). Immunohistochemical staining indicates negative P53-negative expression (G), scattered positive CD34 expression in tumor cells in addition to vascular endothelial cells (H), positive ATRX expression (I), positive Olig2 expression (J), positive Syn and Pan-TRK expression (K, L), positive NSE expression in neurons (M), and positive mutant IDH1 (R132H) expression (N). Scale bar = 50mum.
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T2 weighted magnetic resonance imaging (MRI) of the brain showed an inhomogeneous hyperintense lesion located in the left frontal lobe ( Figure 1A ), measuring 2.0 x 1.5 x 1.7 cm in dimension, while T1 weighted MR image revealed hypo-intensity without peri-tumoral edema ( Figure 1B ). Contrast-enhanced MRI exhibited no significant enhancement ( Figures 1C, D ). The tumor was soft and confined in the lobe ( Figure 1E ). H&E staining revealed a multinodular glial element, and a honeycomb appearance of oligodendrocyte-like cells was observed, with neurons floating in the matrix ( Figure 1F ). Immunohistochemistry analysis showed positive ATRX nuclear stain and negative P53 expression ( Figures 1G, I ), consistent with the genomic analysis showed wild-type ATRX and TP53. Scattered CD34 expression was seen in tumor cells in addition to vascular endothelial cells ( Figure 1H ), which was consistent with a previous report showing frequent CD34 expression in mixed or diffuse DNT. Tumor cells also expressed synaptophysin (Syn) ( Figure 1K ), oligodendrocyte transcription factor 2 (Olig2) ( Figure 1J ), and Ki-67 positivity less than 5%. Neuron-specific enolase (NSE) expression was observed in the neurons as expected ( Figure 1M ). Moreover, Anti-Pan TRK antibody staining revealed a strong signal in tumor cells, consistent with the TrkB rearrangement ( Figure 1L ). IDH1 (R132H) ( Figure 1N ). IDH1 mutations are often seen in diffuse gliomas including astrocytoma or oligodendroglioma but are rarely reported in DNTs.
Characterization of the LHFPL3::NTRK2 fusion. (A) Targeted RNA NGS revealed an LHFPL3::NTRK2 fusion transcript with an intact reading frame. (B) A schematic diagram showed the breakpoints of LHFPL3 and NTRK2, with the fused gene retaining the tyrosine kinase domain of the NTRK2. (C, D) FISH with an NTRK2 split-apart probe showed the separation of the 5' NTRK2 (Red) from the 3' NTRK2 (Green), consistent with the NTRK2 gene rearrangement. (E) RT-PCR confirmed the expression of LHFPL3::NTRK2 fusion transcript. (F) Sanger sequencing of the PCR product confirmed the breakpoints of LHFPL3 and NTRK2 genes. NTC, No Template Control; NC, Negative Control.
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An RNA NGS assay with 390 'bait' probes targeting 63 genes commonly rearranged in solid tumors revealed an LHFPL3::NTRK2 transcript ( Figure 2A ). Figure 2B ). FISH analysis with a break-apart NTRK2 probe confirmed the NTRK2 rearrangement in tumor cell touch preparation ( Figures 2C, D ). The dominant band ( Figure 2E ) was Sanger sequenced and was identical to the transcript obtained from the RNA NGS. A targeted DNA NGS ( Figure 2F ) analysis revealed an isocitrate dehydrogenase 1 (IDH1) mutation (p.R132H) ( Figure 3A ) and copy number gains of the chromosomes 7p, 9q, and X ( Figure 3B ).
DNA NGS results of the tumor. (A) IGV image of the IDH1 mutation (p.R132H). (B) Copy number variation (CNV) analysis showed gains of the chromosomes 7p, 9q, and X with no evidence of 1p/19q co-deletion.
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A targeted DNA NGS ( Figure 2F ) analysis revealed an isocitrate dehydrogenase 1 (IDH1) mutation (p.R132H) ( Figure 3A ) and copy number gains of the chromosomes 7p, 9q, and X ( Figure 3B ).