A clinicopathological analysis of unusual extraventricular neurocytoma of spinal cord

Abstract

Background Extraventricular neurocytoma (EVN) is an unusual tumor and has been recently accepted as a new brain tumor entity by World Health Organization (WHO) classification. It has been reported in several locations outside the typical supratentorial ventricular system, including the cerebral hemispheres, cerebellum, pons, spinal cord, cauda equine and retina. Only a few cases have been
described in the spinal cord in the literature. It is a diagnostic challenge for clinicians and histopathologists to differentiate EVN from other spinal tumors because of its similarities in histological and immunohistochemical findings, as well as its non⁃specific radiological manifestation. Herein we describe a case of unusual intramedullary EVN in spinal cord. The clinicopathology of this tumor and its differential diagnosis are discussed. Methods The clinical manifestation of a patient with primary EVN occurring C6-T3 level of spinal cord was presented retrospectively. Gross totally resected mass was routinely paraffin-embedded and stained with hematoxylin and eosin. Dako EnVision immunohistochemical staining system was used to detect the tumor antigen expressions, including vimentin (Vim), cytokeratin (CK), epithelial membrane antigen (EMA), glial fibrillary acidic protein (GFAP), S-100 protein (S-100), synaptophysin (Syn), chromogranin (CgA), neuron-specific enolase (NSE), Neuronal nuclei (NeuN), oligodendrocytes transcription factor-2 (Oligo-2) and Ki-67. Results A 47-year-old male patient presented with 1 year history of weakness in both upper limbs associated with an increasing neck back pain. There was no paraesthesia in limbs. MRI of the whole spine revealed a heterogeneous intramedullary mass resembling an ependymoma extending from the C6 to T3 level with heterogeneous enhancement after contrast administration. Laminectomy and midline opening of the dura were performed. The spinal lesion appeared to have no capsule and locate intramedullary. The lesion did not attach the dura mater and invade the surrounding tissues. The tumor was removed totally. Microscopic examination showed that a moderate cellular tumor was composed of uniform cells and arranged in sheets. The tumor cells had round nuclei, finely speckled chromatin and clear cytoplasm. Some cells had perinuclear haloes resembling oligodendroglioma. In some areas, the tumor cells with elongated cytoplasmic processes arranged radially around the blood vessels with myxoid degeneration, forming a structure of "perivascular pseudorosette", resembling the ependymoma. Mitotic activity and necrotic area were not observed. The tumor cells were strongly immunopositive for Syn, focally positive for NSE, S-100 and Oligo-2, but negative for Vim, CK, EMA, NeuN and GFAP. Ki-67 index was less than 1% in our case. Based on clinical presentation and histological findings, a final histological diagnosis of primary EVN in spinal cord was made according to the criteria of WHO classification. The patient has not received radiotherapy and attended follow-up for 6 months, without any neurological deficit or signs of recurrence. Conclusion Spinal EVN is extremely rare and there are no more than 20 bona fide cases reported previously all over the world. It might originate from neuronal precursor cells surrounding the region of central canal in fetal life. The definite diagnosis of this tumor should be made under the microscopical examination because the preoperatively radiological appearance of the tumor does not differ from other tumors occurring in spinal cord. Although good prognosis obtained from gross total resection in most of reported patients with this tumor, adjuvant radiotherapy is recommend for those tumors with atypical histological features to avoid the tumor recurrence. Due to the rarity of its site, the tumor can easily be confused with other tumors of spinal cord with clear cells features and ependymoma-like structure. The strictly differential diagnosis should be made when the tumor is encountered in spinal cord.