PAPILLARY GLIONEURONAL TUMOR - A NEW VARIANT OF MIXED NEURONAL-GLIAL NEOPLASM

We describe the clinicopathologic features of nine cases of a unique p apillary glioneuronal tumor (PGNT) exhibiting astrocytic as well as ex tensive and varied neuronal differentiation. The four male and five fe male patients studied ranged in age from 11 to 52 years (mean 27.7 yea rs). They either presented with mild neurologic symptoms or were asymp tomatic. Magnetic resonance imaging showed demarcated cystic, 1.5-cm t o 7-cm contrast-enhancing masses; five involved the temporal lobe, two the parietal, and two the frontal. All but one were totally resected. No recurrence was noted despite a follow-up period of 3 years. Two mi croscopic components were evident: 1) compact pseudopapillae composed of hyalinized vessels covered by a single layer of glial fibrillary ac id protein (GFAP)-positive astrocytes and 2) synaptophysin-positive ne uronal cells of varying size, including neurocytes, ganglioid cells, a nd ganglion cells within neuropil. Immunostains for chromogranin-A wer e negative, as was in situ hybridization for chromogranin-A mRNA. Ultr astructurally, neuronal cells featured microtubule-containing processe s and aberrant synaptic terminals, but dense core granules were rare. Overall, cellularity was moderate and atypia was minimal. No mitotic a ctivity or necrosis was noted. The proportions of the two components v aried, but essential morphologic findings were identical in all cases. In that the clinical, radiographic, and morphologic characteristics o f PGNT mt distinctive, it appears to represent a previously undescribe d form of mixed neuronal-glial tumor of the central nervous system.