Epilepsy-associated brain tumors.

Abstract Brain tumors represent a frequent finding in patients with chronic, intractable focal epilepsies. The majority of these long-term epilepsy-associated tumors do not show a malignant progression and reveal an unusual histological architecture with dysplastic neurons, neoplastic glial cell elements as well as low proliferation indices. A review of a large series of 4512 samples obtained from the German Neuropathological Reference Center for Epilepsy Surgery revealed that gangliomas and dysembryoplastic neuroepithelial tumors are the most abundant entities and account for approximately 61% of all surgically resected tumors. The availability of surgical tissue specimens opens up the possibility of addressing the origin and epileptogenicity of epilepsy-associated tumors. Intriguingly, most studies failed to identify common tumor suppressors or oncogenes. In contrast, neurodevelopmentally regulated molecules, i.e., the insulin growth factor receptor or reelin signaling pathways, are likely to be aberrantly activated or downregulated. Further systematic research strategies addressing these peculiar tumors will, therefore, also foster our understanding of brain development under physiological as well as pathophysiological conditions.