Simple and complex dysembryoplastic neuroepithelial tumors (DNT) variants: clinical profile, MRI, and histopathology.

INTRODUCTION: Dysembryoplastic neuroepithelial tumors (DNTs) are long-term epilepsy associated tumors subdivided into simple and complex variants. The purpose of this study was to relate different DNT components identified on magnetic resonance imaging (MRI) to histopathological features and to test the hypothesis that glial nodules as a histopathological feature of complex variants induce an occasional glioma misdiagnosis. METHODS: Clinical, MRI, and histopathologic features of DNTs operated between 1988 and 2008 were reviewed. RESULTS: From a total of 61 DNTs, 48 simple and 13 complex variants were identified. Multiple or single pseudocysts in a cortical/subcortical location with small cysts sometimes separated from the tumor represented the glioneuronal element and were found in all DNTs. FLAIR hyperintense tissue was found between pseudocysts but--in neocortical DNTs--also circumscript in deeper tumor parts. Calcification and hemorrhages in this location occurred in four of 13 complex variants, and one of these patients was also the only one with tumor growth. Patients with complex variants had earlier seizure onset, and complex variants were more often located outside the temporal lobe. Although complex variants represented a higher diagnostic challenge, misdiagnoses also occurred in simple variants. One of five of DNTs showed contrast enhancement, which varied on follow-up studies with enhancing parts becoming nonenhancing and vice versa. CONCLUSION: The glioneuronal element is readily identifiable on MRI and should be considered to support the DNT diagnosis. Complex DNT variants have a different clinical profile and a more variable histopathological and MRI appearance; however, misdiagnoses occasionally also occur in simple variants.