Dysembryoplastic neuroepithelial tumor: report of a case without typical glioneuronal elements.

We studied a temporal lobe lesion found in a 44-year-old woman with a 25-year history of intractable complex partial seizures. Histologically, the lesion contained several nodular areas differing in cellular composition within the disarranged uncal cortex; in each area, neuronal and small round cells, mature ganglion cells and fibrillary astrocytic cells predominated. Ultrastructurally, the small round cells demonstrated neuronal, astrocytic or oligodendrocytic features. The astrocytic cell processes were occasionally covered by basal laminae. The mature ganglion cells had well-developed rough endoplasmic reticulum, many mitochondria and lipofuscin granules in their cytoplasm. No dense-cored vesicles were evident. We diagnosed this temporal lobe lesion as a dysembryoplastic neuroepithelial tumor (DNT), although no areas of typical glioneuronal elements with mucinous matrix were evident. This case suggests that a glioneuronal element is not always a constant feature of DNT, and that although mature ganglion cell nodules may be present, they may differ from those of gangliocytomas and gangliogliomas in lacking intracytoplasmic dense-cored vesicles. The presence of occasional astrocytic cell processes covered by basal laminae strongly suggests that some of the constituent astrocytic cells were of subpial astrocytic origin.