Glioneuronal tumor with neuropil-like islands

Mixed glioneuronal neoplasms are relatively uncommon tumors in the central nervous system. Recently, an unusual glioneuronal tumor arising in adults m arked histologically by neuropil-like islands was described. We present a s imilar case arising in a 23-year-old woman who presented with headaches and seizures and on imaging studies was noted to have a frontal-temporal lobe mass. The patient underwent partial resection of the tumor, which histologi cally resembled anaplastic astrocytoma, and received a course of radiation therapy and chemotherapy. increasing seizure frequency and expanding size o n neuroimaging prompted a re-excision of the tumor. The second resection wa s marked by islands of tissue resembling gray matter with slightly atypical neuronal and glial cells situated in the white matter. These islands stain ed positively with synaptophysin and did not stain with glial fibrillary ac id protein. Mild vascular proliferation and moderate nuclear pleomorphism a lso characterized the tumor. Areas of necrosis were not noted, A MIB-1 labe ling index of 18.1% was noted. P53 immunoreactivity was observed in approxi mately 40% of tumor cell nuclei, This lesion is felt to represent a clinica lly aggressive glioneuronal neoplasm with an unusual and distinctive histol ogic phenotype. HUM PATHOL 31:1435-1438. Copyright (C) 2000 by W.B. Saunder s Company.