Dysembryoplastic Neuroectodermal Tumors

Abstract

Dysembryoplastic neuroectodermal or neuroepithelial tumor (DNET) was initially described by Daumas-Duport et al. [5] in 1988 as a mixed tumor with glial and neuronal elements, and has been included in the World Health Organization classification of brain tumors as a separate entity [11]. It is considered as hamartomatous, low-grade lesion (WHO grade I) due to the dysplastic appearance of the lesion and the surrounding cortex. It constitutes about 1.5% of all pediat-ric intracranial tumors. They mainly occur in the temporal lobe followed by the frontal and occipital lobe or the cerebellum and brain stem [16]. Macroscopically, DNETs are most of the time confined to the cerebral cortex, but may extend into the adjacent white matter. DNETs typically manifest during childhood or early adulthood with often medically refractory epileptic seizures. The seizure focus is frequently in the temporal location, and the lesion most often found in the temporal lobe, followed by the frontal lobes, and is only rarely located in other lobes. Associated cranial bone deformities with thinning of the overlying calvarium may be present. Histologically, DNETs are characterized by the presence of a specific element and by a nodular component. The specific elements consist of oligoden-droglia-like cells that are distributed within a mucinous matrix, in which normal and dysplastic ganglion-like neurons appear to be floating (“floating neurons”). Although increased cellularity and some pleomorphism may be present, these lesions are devoid of anaplastic features. Based on the results of immunohistochemical studies, DNETs are considered to originate from progenitor cells with potential for glial and neuronal differentiation. The surgical outcome is excellent. Even after subtotal resection recurrences are rare.