Dysembryoplastic neuroepithelial tumors. Features in eight cases, including two with unusual locations.

Objectives. - Dysembryoplastic neuroepithelial tumors (DNTs) are usually lo cated within the supratentorial cortex. We present a series of eight cases of DNTs including two cases with an extracortical location, one in the caud ate nucleus, the other one expanded in the lateral ventricule, septum and f ornix. An origin from secondary germinal layers, as previously suggested, c an explain these extracortical locations. Material and methods. - Of the eight patients; seven had partial epileptic seizures es and one intracranial hypertension. All patients underwent clini cal examination, a computed tomographic (CT) scan, a magnetic resonance ima ging (MRI) and a surgical removal of the lesion with histological examinati on. Results. - Clinical examination was normal except in the case with intracra nial hypertension where a bilateral papillary oedema was found In seven cas es the CT scan showed a hypodense lesion of pseudocystic appearance. All le sions were hypointense on T2-weighted and hyperintense on T2-weighted MRI. Contrast enhancement was observed in two cases. The lesion was intracortica l in six cases and extracortical in the remaining two : one in the head of the caudate nucleus and one in the trigo-noseptal region. Histological exam ination identified an appearance of DNT with a specific glioneuronal elemen t in six cases. Conclusion. - The diagnosis of DNT can be suspected before histological exa mination on radiological features, chiefly because the tumor is located in the supratentorial cortex. However, extracortical locations no exist, even if unusual. As DNTs are always benign, knowledge and accurate diagnosis of these atypical cases are mandatory in order to avoid useless and even delet erious additional treatments, such as radiotherapy.