GLIONEUROCYTOMA - TUMOR WITH GLIAL AND NEURONAL DIFFERENTIATION

We report two cases of low-grade glioma in which multiple cellular com ponents, including cells with dense-core granules consistent with ''ne urocytes,'' were identified on electron microscopic studies. The first patient was an apparently normal boy until the onset of seizures at a ge 10 months. Initially, the seizures improved with phenobarbital trea tment, but good seizure control was never achieved. Computed tomograph ic scan at age 23 months showed a calcified, nonenhancing left parieta l mass. This tumor was composed of sheets of cells with clear cytoplas m and round to oval nuclei. Mucinous intercellular material stained po sitively with periodic acid-Schiff, mucicarmine, and alcian blue stain s. Foci of calcification were evident. The second patient was a 13-yea r-old boy with a left parasagittal parieto-occipital mass who presente d with a 4-month history of seizures and declining school performance. The tumor was composed of sheets of astrocytes with dark, hyperchroma tic, pleomorphic nuclei in a fibrillary and microcystic background. Th e tumor contained the pleomorphism seen in the adult variant of pilocy tic astrocytoma, as well as the microcystic component seen in the juve nile variety. Ultrastructurally in both cases, there were occasional t umor cells having round to oval nuclei with moderate amounts of cytopl asm containing 150- to 250-nm-diameter dense-core granules. These cell s were admired with the majority of tumor cells, which in case 1 had t he ultrastructural features of astrocytes and oligodendrocytes and in case 2 had features of protoplasmic or pilocytic astrocytes. Our cases bear superficial resemblance to dysembryoplastic neuroepithelial tumo rs; however, dysplastic ganglion cells are an essential component for that diagnosis, and there were no dysplastic ganglion cells in either of our cases. Cells containing dense-core granules (neurocytes) were f ound in both our cases by electron microscopy and appear to be a part of a neoplastic process. The significance of neurocytes in low-grade g liomas is not known. Cerebral tumors consisting of neuroblasts/neurocy tes in toto or in part have been increasingly recognized in recent yea rs, and our cases add to the spectrum of such neoplasms.