Neoplasms resembling subependymal giant cell astrocytomas (SEGA) typical of tuberous sclerosis occur in a subset of individuals with NF1, although they tend to be hemispheric (a, b,c). As SEGA, they express glial markers (GFAP, d; OLIG2, e) and neuronal markers (synaptophysin, f). SEGA-like astrocytoma in NF1 patient (g) with intact ATRX expression (h) but large telomere foci (red) colocalizing with Promyelocytic bodies (green)(arrow) consistent with alternative lengthening of telomeres (i).