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case_images: (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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case_images: 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.
case_images: 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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case_images: 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 ).
case_images: 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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case_images: 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 ).