Central neurocytoma. A clinicopathological, immunohistochemical and ultrastructural study of 7 cases.

Characterised by distinctive clinicopathological features, the central neurocytoma (CN) is an uncommon and possibly under-recognised primary cerebral neuronal neoplasm. We present clinical and pathological details of seven patients with CN. Histological examination revealed a greater diversity of morphological appearances than is typically described in CN. No anaplastic features were identified. Cellular areas resembling both oligodendroglioma and ependymoma were present in all cases, but each tumour also contained stroma rich areas with hyalinised or aneurysmal vessels. Synaptophysin was expressed by all tumours and probably represents the immunohistochemical marker of choice for identifying CN. Distinguishing ultrastructural features included rounded cell bodies separated by numerous cell processes containing microtubules, pleomorphic neurosecretory granules and occasional synapses. Ki-67 immunostaining revealed a low cell proliferation index in each case. The distinction of CN from other pathological mimics can be reliably made using this multiparametric approach to diagnosis. The generally benign behaviour of CN is confirmed, though there was one patient death in the follow-up period of 10-122 months. Aggressive behaviour in this case was not associated with anaplastic histological features.