Dysembryoplastic neuroepithelial tumors: nonspecific histological forms - A study of 40 cases

Objective. To demonstrate that DNTs include a large morphological spectrum of tumors that cannot be histologically distinguished from conventional cat egories of gliomas. Methods. All tumors from patients who underwent epilepsy surgery in Sainte- Anne hospital (Paris) that histologically resembled gliomas and did not con form to current histological criteria for DNTs or gangliogliomas were enter ed in the study. Results, According to the WHO histological classification, the 40 tumors re sembled: pilocytic astrocytomas (4 cases), astrocytomas (16 cases), anaplas tic astrocytoma (1 case), oligodendrogliomas (10 cases), oligo-astrocytomas (8 cases) or anaplastic oligo-astrocytomas (1 case). However foci of corti cal dysplasia could be observed in 47% of the cases. Clinical presentation and imaging features were strikingly similar to that observed in typical DN Ts. Although surgical removal was incomplete in 28% of the cases and none o f the patients underwent chemo or radiotherapy, none of the tumors recurred (mean follow-up: 7 years). Moreover, serial preoperative imaging in 26 pat ients (mean follow-up: 4.5 years) demonstrated that these lesions were perf ectly stable. Conclusions. Whatever the histological appearance of a glial tumor, the dia gnosis of DNT must be considered when all the following criteria are associ ated: (1) partial seizures, with or without secondary generalization, begin ning before the age 20 years, (2) no neurological deficit or stable congeni tal deficit, (3) cortical topography of the lesion as better demonstrated b y MRI and (4) no mass effect on imaging.