PRIMITIVE NEUROECTODERMAL TUMOR OF THE MENINGES - AN HISTOLOGICAL, IMMUNOHISTOCHEMICAL, ULTRASTRUCTURAL, AND CYTOGENETIC STUDY

We report a case of primitive neuroectodermal tumor (PNET) arising fro m the meninges in a 30-yr-old female patient whose clinical and radiol ogical features were consistent with meningioma. The neoplasm was comp osed of primitive small, round cells, growing in sheets and nests in c ontinuity with meningeal layers. Ultrastructurally, the neoplastic cel ls were characterized by large and regular nuclei, primitive cytoplasm with pools of glycogen, and lack of dense core granules. The neuroect odermal nature of the tumor was confirmed by positive immunostaining f or vimentin, neurofilaments, neuron specific enolase (NSE), and 013 (a n antibody raised against MIC2 antigen). Further support to the diagno sis was obtained by reverse transcriptase-polymerase chain reaction (R T-PCR) detection of Chromogranin A and Secretogranin II genes. t(11;22 ) translocation was also observed by RT-PCR, a finding that was not re corded in previously described intracranial PNET. The tumor followed a malignant course, recurring and spreading to chest wall and sacro-ili ac region over a 10-yr period. The meningeal location enlarges the top ographic spectrum of intracranial PNET, and this tumor has to be consi dered in the differential diagnosis with meningioma.