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The World Health Organisation (WHO) classification of brain tumours now includes the entity central neurocytoma as originally defined by Hassoun et al in 1982.1 Typically the tumour occurs in a supratentorial location in or around the lateral ventricles. Six cases of central neurocytoma of the spinal cord have been reported to date.2-4 We report a further case to highlight the importance of recognising this lesion at this site because the prognosis, as with central neurocytomas elsewhere, seems to be highly favourable.
A 12 year old boy presented with an eight week history of interscapular pain at night, after a fall. This was accompanied by numbness of the left arm and paraesthesiae of both hands coupled with fatigue in the legs. There had been no sphincteric symptoms. There had been no perinatal difficulties and he had reached his developmental milestones appropriately. On examination there was a symmetric proximal grade 4/5 weakness of the upper limbs and a reduction in sensation in both arms corresponding to the C5, C6, and C7 root distributions.
Brain MRI (fig 1) showed a well defined, partially cystic, intramedullary mass with areas of gadolinium enhancement extending from the level of C4 to T1. He underwent a lower cervical laminotomy and complete resection of the tumour. His postoperative course was complicated only by transient left arm pain which responded to carbamazepine. He remains well with no neurological deficits at 24 months of follow up.
Histologically the tumour comprised sheets of uniform polygonal cells entrapped in a highly collagenised vascular network. Tumour cells had small round nuclei and delicate stippled chromatin, their cytoplasm contained a small eosinophilic crescent, or more often formed a perinuclear halo. A few cells with larger vesicular nuclei, prominent nucleoli, and more copious cytoplasm with Nissl substance suggested ganglionic differentiation (fig 2). Occasional foci of eosinophilic fibrillary tissue were scattered among the tumour cells. Mitotic activity and necrosis were not seen.
Immunohistochemically the tumour cells were negative for glial fibrillary acidic protein (GFAP) but strongly positive for synaptophysin, protein gene product 9.5 (PGP 9.5), and neuron specific enolase (NSE). These morphological and immunohistological features suggested the diagnosis of central neurocytoma.
Although the term central neurocytoma is generally restricted to tumours of the supratentorial ventricular system several reports of this tumour occurring in extraventricular sites have appeared.5 Seven cases of “central neurocytoma” have now been described occurring in the spinal cord.2-4 Such a diagnosis is based on the immunohistochemical profile of the lesions showing neuronal differentiation. The principal differential diagnoses in our case, ependymoma and oligodendroglioma, are excluded by virtue of their immunohistochemical profile.
It has been suggested that the cell of origin of the central neurocytoma arises in the periventricular germinal matrix6and this may account for the finding of these tumours in the spinal cord, arising from the region of the central canal.
Most reported cases of central neurocytoma occur in adolescents or young adults. A review of the cases occurring in the spinal cord shows a wide range of ages (12–67 years). The numbers are too few to draw any firm conclusions but several cases have occurred at a young age.
As with supratentorial examples of central neurocytoma, the clinical behaviour seems to run a benign course in cases involving the spinal cord. The two cases reported by Tatter et al 3received radiotherapy; however, it remains to be seen whether or not this is necessary in most cases. In view of the benign histological appearances (unless there are malignant histological features or aggressive tumour behaviour making the diagnosis of central neurocytoma less likely) we think that postoperative adjuvant radiotherapy should be avoided, particularly in the younger age group with a still growing skeleton.
This case is documented to highlight the importance of recognising central neurocytoma in extraventricular sites as it carries a good prognosis.