In the present study, to clarify differences in the amounts and interactions of extracellular Glu, CD44, xCT, and EAAT2 in the tumor periphery of GBM patients with and without epilepsy, we investigated the expressions of these molecules and analyzed the interrelationships by comparing expressions between GBM tissues collected from the core and periphery in patients with and without epilepsy. Here, CD44 is linked to epilepsy.