Fig. 2

Illustration of a pediatric case of FGFR3::TACC3 low grade glioma (#22 & #14). Upper panel a–e illustrates the case of a 1-year-old at diagnosis child (#22). Clinical presentation was a West syndrome starting at 6 months of life. MRI revealed a left temporal infiltrative tumor (a T1 with gadolinium injection; b FLAIR sequence). Surgical resection was performed at 1 year old. Histological examination c showed a diffuse glial tumor with calcifications, there was no microvascular proliferation, no necrosis, nor mitotic activity. There was no CD34 extravascular expression (d). Methylation class with v12.5 was ganglioglioma with a calibrated score of 0.39, and the case clustered with ganglioglioma cluster on t-SNE, it fell within cluster 1 with other low-grade tumors on hierarchical clustering. Copy number plot generated by the platform did not show copy number variation (e). Lower panel f–i illustrates the case of a 12-year-old child (#14) with chronic epilepsy. MRI show a left temporal without contrast enhancement (f T1 with gadolinium injection, g FLAIR sequence), surgical resection at 12 years old and revealed a diffuse oligodendroglioma-like tumor with calcification and strong and diffuse CD34 expression and FGFR3(ex17)::TACC3(ex13) fusion, very suggestive of a polymorphous low grade neuroepithelial tumor of the young (PLNTY) in the absence of ganglion cells (h hematoxylin–phloxin–saffron). There was no TERT promoter mutation and no chromosome + 7/− 10 (i CNV plots from DNA methylation profiling). Methylation class was ganglioglioma with 0.99 calibrated score. Scale bars: 50 µm