OLIG2 and epilepsy: It is recognised that low-grade epilepsy-associated tumours can widely extend along the subpial layer and layer I in the adjacent cortex (Blumcke et al., 2019); the significantly higher Olig2 and GFAP/MCM2 densities noted in FCD3b could arguable reflect tumour progenitor cell infiltration along superficial layers rather than co-existing dysplasia.