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Neurology India, Vol. 59, No. 4, July-August, 2011, pp. 648-649 Letter to Editor Primary thoracic primitive neuroectodermal tumor mimicking as neurofibroma PK Nayak1, K Mohini Rao2, GC Sahoo3, AK Mahapatra4 1 Department of Neurosurgery, Neelachal Hospital and Hi-Tech Medical College, Bhubaneswar, Orissa, India PMID: 21891963 DOI: 10.4103/0028-3886.84367 Primitive neuroectodermal tumor (PNET) is a group of histologically indistinguishable neoplasm and can occur at any part of the neuroaxis. [1] In the recent years, PNETs have been increasingly reported; however, reports of spinal location are very few. [2] Primary epidural PNETs are very rare. An 18-year-old female presented with progressive weakness of both lower limbs over a period of 3 months. Motor power in lower limbs was 4/5, and deep tendon jerks were exaggerated. The sensory level was approximately at T4 level. Magnetic resonance imaging of thoracic spine showed a dumbbell-shaped tumor at D1 and D2 level with epidural component, isointense on T1W and hyperintense on T2W sequence with homogenous contrast enhancement [Figure - 1] and [Figure - 2] The left paraspinal and posterior mediastinal components were in continuity through the neural canal foramen. The epidural component was compressing and shifting the spinal cord toward right side. The provisional diagnosis was neurofibroma. Computer tomography scan of brain was normal. Near-total tumor excision was performed under operating microscope. Tumor was grayish yellow, firm, moderately vascular, and easily separable from the surrounding tissue. There was no invasion of the dura. The postoperative period was uneventful. Pathologic examination of the mass showed, hypercellular, malignant, small, round blue cells arranged in loose clusters, with fibrillary background. Cell showed few rossettes, mitosis, and apoptosis with focal areas of necrosis. Sheets of cells were separated by septa and vascular tissue. The tumor cells were immunopositive for microneme protein 2 (MIC-2), while were negative for cytokeratin, desmin, myogenin, and leucocyte common antigen. The thoracic part was treated by radiotherapy and chemotherapy. PNETs are derived from the primitive neural crest cell and are highly malignant. These tumors are reported mostly in the central nervous system, chest wall, lower extremities, trunk, kidney, orbit, and rarely in the spine. [3] PNET is defined as an embryonal tumor composed of undifferentiated or poorly differentiated neuroepithelial cells that have the capacity for divergent differentiation into neuronal astrocytic, ependymal, muscular, and melanotic lines. [4] These tumors commonly occur in cerebellum but can arise in the pineal gland, cerebrum, spinal cord, brain stem, and peripheral nerves. [5] Primary intraspinal PNETs may arise at all levels of the spine and can be intramedullary, extramedullary, or extradural. PNETs are rapidly growing tumors with a brief duration of symptoms and rapidly progressive course. [6] Spinal PNETs are more common in adults. Some times these tumors may metastase, most frequent sites being lungs, bones, and lymph nodes. [2] Primary epidural PNETs may be classified as a subtype of spinal PNETs. In our patient the tumor was around the vertebrae and occupied the spinal canal without penetrating the dura. Diagnosis is made by excluding readily classified small round cell neoplasms and then demonstrating the neural origin of the tumor by means of ultrastructural or immunocytochemical studies. [7] PNETs and Ewing's sarcoma are closely related, so also the round-cell tumors of soft tissue and bones. They strongly express the glycoprotein p30/32 (CD99), which are encoded by the MIC-2 genes. Because of immunohistochemical, ultrastructural, and molecular biologic similarities, both have recently been categorized into the Ewing sarcoma family of tumors. [3] The prognosis of these tumors is very poor and its treatment is far from satisfactory. Radical resection combined with radiation therapy and chemotherapy is preferred treatment and leads to better outcomes. [7] Adjunctive immunotherapy is currently being investigated as a possible therapy. [2] The causes of death include metastatic disease, aggressive local spread, and progressive spinal cord involvement. [2] 8F-fluoro-2-deoxy-glucose positron emission tomography is an effective imaging modality for evaluating suspected tumor recurrence. [8] References
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