DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOR - A TUMOR WITH SMALL NEURONAL CELLS RESEMBLING OLIGODENDROGLIOMA

Dysembryoplastic neuroepithelial tumor (DNT) is a clinicopathologicall y unique group of tumors, mostly located in the temporal lobe, associa ted with intractable complex partial seizure in young patients. We rep ort two unusual cases with multifocal involvement of diverse sites in the central nervous system. Case 1 is that of a 50-year-old man with g -year history of grand mal seizures, who died of acute myocardial infa rction. Case 2 is that of a 10-year-old girl with intractable complex partial seizures and behavioral disorder. Postmortem examination in ca se 1 showed multifocal tumor in the left temporal lobe, third ventricl e, and basal ganglia. Magnetic resonance imaging in case 2 showed tumo r in the right temporal lobe, both thalami, right cerebellar hemispher e, and pens. Histologically, both tumors were characterized by a multi nodular appearance with a predominant component of alveolar arrangemen t of oligodendroglial-like cells around delicate capillaries, with muc oid matrix containing floating gan glion cells. There were also astroc ytic nodules resembling pilocytic astrocytoma in case 1, and a ganglio cytoma-like area merging with surrounding cortical dysplasia in case 2 . Ultrastructural examination showed ganglionic differentiation in the oligodendroglial-like cells in case 2. They possessed dense core neur osecretory granules and many slender neuritic processes with microtubu les arranged in parallel and terminating in synaptic junctions. The pe riventricularly located tumor with nodular extension to the periphery suggests an origin from subependymal germinal matrix with nests of pri mitive neuroblasts arrested in their embryonal migration. DNTs are rel ated to ganglioglioma based on their common location and clinical beha vior and on the presence of voth ganglionic and astrocytic cells. They are also related to pilocytic astrocytoma by morphological and behavi oral similarity. Together with cerebral neuroblastoma and central neur ocytoma, they form a spectrum of tumors harboring small neuronal cells . The differentiation of DNT from oligodendroglioma is important so as to avoid unnecessarily aggressive therapy.