Primitive Neuroectodermal Tumor of the Meninges: An Histological, Immunohistochemical, Ultrastructural, and Cytogenetic Study.

We report a case of primitive neuroectodermal tumor (PNET) arising from the meninges in a 30-yr-old female patient whose clinical and radiological features were consistent with meningioma. The neoplasm was composed of primitive small, round cells, growing in sheets and nests in continuity with meningeal layers. Ultrastructurally, the neoplastic cells were characterized by large and regular nuclei, primitive cytoplasm with pools of glycogen, and lack of dense core granules. The neuroectodermal nature of the tumor was confirmed by positive immunostaining for vimentin, neurofilaments, neuron specific enolase (NSE), and 013 (an antibody raised against MIC2 antigen). Further support to the diagnosis was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) detection of Chromogranin A and Secretogranin II genes. t(1 1;22) translocation was also observed by RT-PCR, a finding that was not recorded in previously described intracranial PNET. The tumor followed a malignant course, recurring and spreading to chest wall and sacroiliac region over a 10-yr period. The meningeal location enlarges the topographic spectrum of intracranial PNET, and this tumor has to be considered in the differential diagnosis with meningioma.