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Primitive Neuroectodermal Tumor of the Meninges: An Histological, Immunohistochemical, Ultrastructural, and
Mauro Papotti1, Giancarlo Abbona, Alberto Pagani
1MD, FRCPATH.
Abstract:
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.
Insights
This study describes a rare case of primitive neuroectodermal tumor (PNET) originating in the meninges, initially mimicking meningioma. The PNET exhibited aggressive behavior and unique genetic findings, expanding the known locations for this type of brain tumor.
Area of Science:
- Neuro-oncology
- Pathology
- Genetics
Background:
- Primitive neuroectodermal tumors (PNETs) are rare malignant neoplasms of the central nervous system.
- PNETs typically arise in the cerebrum, cerebellum, or spinal cord.
- Meningiomas are common, benign tumors arising from the meninges.
Purpose of the Study:
- To report a unique case of meningeal PNET.
- To highlight the diagnostic challenges and differential diagnosis with meningioma.
- To characterize the molecular and ultrastructural features of this rare tumor.
Main Methods:
- Histopathological examination of tumor tissue.
- Immunohistochemical staining for neuroectodermal markers (vimentin, neurofilaments, NSE, O13).
- Ultrastructural analysis via electron microscopy.
- Reverse transcriptase-polymerase chain reaction (RT-PCR) for gene expression (Chromogranin A, Secretogranin II) and chromosomal translocation t(11;22).
Main Results:
- The tumor presented with clinical and radiological features suggestive of meningioma.
- Histopathology revealed small, round, primitive cells with neuroectodermal features.
- Immunohistochemistry and ultrastructural analysis confirmed the neuroectodermal origin.
- RT-PCR detected Chromogranin A, Secretogranin II, and the novel t(11;22) translocation.
- The PNET demonstrated aggressive behavior with recurrence and metastasis over 10 years.
Conclusions:
- Meningeal PNET is a rare entity that can mimic meningioma.
- This case expands the known topographic spectrum of intracranial PNET.
- The presence of t(11;22) translocation is a novel finding in intracranial PNET.
- Early recognition and differential diagnosis are crucial due to the tumor's malignant potential.