Fig. 1

Brain MRI and histopathologic features of patients with somatic variants a Patient F08 at 3 years (FCD type IIB, an MTOR in-frame variant), b, c patient F61 at 2 years (FCD type IIB, germline and somatic variants of TSC2), d patient F48 at 23 years (FCD type IB, a MAP2K1 in-frame deletion), e patient F70 at 21 years (ganglioglioma, deletion of entire chromosome 9), and f patient F30 at 2 years and 7 months (hippocampal sclerosis, 19p13.3p12 deletion). a, b, c, e are T2-weighted axial brain MRIs, and d, f are fluid-attenuated inversion recovery coronal MRIs. Brain MRI showing focal irregular gyri (arrows) with blurred junctions between the cortex and white matter (a) or hyperintensity of the subcortical white matter (b–e). g Patient F67 (FCD type I, a PTPN11 missense variant). Cytoarchitectural abnormality of the cortex. h Patient F08 with FCD type IIB showing several balloon cells in the white matter. i Patient F61 with FCD type IIB exhibiting dysmorphic neurons and balloon cells (arrows) in the cortex. j, k Patient F70 with ganglioglioma. j Astrocytic cells showing a wavy, fascicular arrangement with mild hypercellularity. A dysmorphic ganglion cell (inset in k). k CD34-immunopositive cells with fine processes. g, i and inset in k: Klüver–Barrera stain. h, j hematoxylin and eosin stain. k immunostained and counterstained with hematoxylin. Scale bar = 350 μm for g, 90 μm for h and i, 180 μm for j, 50 μm for inset in k, and 140 μm for k