Neurol India Home 

Year : 2012  |  Volume : 60  |  Issue : 3  |  Page : 335--337

Supratentorial intraparenchymal schwannoma mimicking a glial tumor

Praveen Sharma1, Amit Mahore2, Ritesh Kansal2, Sridhar Epari3, Naina G Kataria4,  
1 Department of Radiotherapy, Tata Memorial Hospital, Mumbai, India
2 Department of Neurosurgery, King Edward Memorial Hospital, Mumbai, India
3 Department of Neuropathology, Tata Memorial Hospital, Mumbai, India
4 Department of Neuropathology, King Edward Memorial Hospital, Mumbai, India

Correspondence Address:
Amit Mahore
Department of Neurosurgery, King Edward Memorial Hospital, Mumbai

How to cite this article:
Sharma P, Mahore A, Kansal R, Epari S, Kataria NG. Supratentorial intraparenchymal schwannoma mimicking a glial tumor.Neurol India 2012;60:335-337

How to cite this URL:
Sharma P, Mahore A, Kansal R, Epari S, Kataria NG. Supratentorial intraparenchymal schwannoma mimicking a glial tumor. Neurol India [serial online] 2012 [cited 2021 Oct 22 ];60:335-337
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A 25-year-old man presented with a history of occipital headache of 6 weeks duration and a single seizure 4 weeks before admission. He had no neurologic deficit or neurocutaneous markers. Computed tomography (CT) of brain revealed a cystic lesion with a mural nodule in the right parieto-occipital lobe [Figure 1]a and b. Magnetic resonance imaging (MRI) showed a well-defined cystic lesion (5.7 s 3.4 cm) with a solid mural nodule lateral to the occipital horn of right lateral ventricle. [Figure 1]c and d. The provisional diagnosis was pilocytic astrocytoma or pleomorphic xanthoastrocytoma. He underwent right parieto-occipital craniotomy and excision of the tumor through transcortical trans-sulcal approach. The cyst contained xanthochromic fluid and the mural nodule was firm, gray, and vascular, which was totally excised. Histology, the tumor was composed of compact fascicles of elongated spindle cells with focal areas of loose stroma [Figure 2]a-c. No Rosenthal fibers or eosinophilic granular bodies were identified. Differentials of pilocytic astrocytoma and schwannoma were considered at this stage. Subsequent ancillary methods showed a rich intratumoral pericellular network of reticulin [Figure 2]d, immune-reactivity for S-100 protein [Figure 2]e, glial fibrillary acidic protein [Figure 2]f, CD 56 (N-CAM), whereas it was immunonegative for p53 protein. Finally, in view of the absence of Rosenthal fibers and diffuse, rich intratumoral pericellular reticulin network, the diagnosis of schwannoma was favored. Brain MRI done at followup showed complete excision of tumor with gliosis at the site of surgery [Figure 1]e. The patient had no added neurologic deficit after 18 months of surgery.{Figure 1}{Figure 2}

Schwannomas are benign tumors arising from the Schwann cells, which produce the myelin sheath around the peripheral nerves, therefore schwannomas are most commonly seen in the peripheral nervous system. [1],[2],[3] Intra-axial ectopic schwannomas unrelated to cranial nerves are extremely rare. [3],[4],[5],[6] The occurrence of these tumors in the intraparenchymal location is a curious entity as the Schwann cells are not native to the central nervous system. [1],[2],[3] Many hypotheses suggesting its developmental origin and otherwise have been suggested. [2],[3] Disordered embryogenesis, failed migration of the neural crest cells, ectopic Schwann cell rests, and derivation from differentiation of multipotent mesenchymal neural crest cells or schwannosis (a term coined by Russell and Rubinstein for hamartomatous lesions consisting of Schwann cells) are some thoughts; however, the facts still remain unclear. [1],[2],[3] There are no pathognomic radiologic features described; however, the reported features include calcification, cyst formation, gliosis, and superficial or periventricular location. [7],[8]

Microscopically these tumors are characterized by 2 tissue types. [2],[7] Antoni type A tissue shows fascicles of spindle-shaped Schwann cells streaming around numerous acellular, eosinophilic areas surrounded by paralleled or palisaded spindled cells with blunt, elongated nuclei occasionally forming Verocay bodies. The second tissue type, Antoni type B, lacks the Verocay bodies and consists entirely of less cellular and more randomly arranged spindle cells in a loose, myxomatous stroma. S100 protein is a diagnostic histochemical marker for schwannoma, however, is not exclusive. [1],[2],[7] Differentiating schwannoma from other tumors is a difficult challenge because of its uncharacteristic clinical presentation, and radiologic and routine light microscopy appearances. [2],[5],[6],[7],[8] Wherever resources permit, immunohistochemistry and ultrastructural features (electron microscopy) of typical interdigitating cytoplasmic processes covered by a basement membrane and special stains, such as Leu 7 and calretinin, may help in providing the diagnosis. [2],[3],[7]

Intra-axial schwannomas may rarely present as cystic lesions with mural nodules and can be easily mistaken for other low-grade tumors, such as pilocytic astrocytomas or pleomorphic xanthoastrocytoma. It is important to recognize this tumor due to its benign nature, resemblance to glial tumors, and an excellent response to resection alone.


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