Atypical central neurocytoma: report of a case.

Central neurocytomas are rare, relatively benign intraventricular neoplasms composed of uniform round cells with neuronal differentiation. The majority of previously reported central neurocytomas did not recurr after tumor removal and the patients had favorable postoperative outcomes. Only a few cases with malignant histopathology or malignant behavior have been noted. Atypical central neurocytoma is a new entity that was first described in the literature in 1997. The tumors have been noted to exhibit a Ki-67 labeling index of 2% or more, or vascular proliferation, mitoses, and necrosis, or both. Atypical histologic findings are usually associated with a somewhat less favorable clinical course and requires postoperative radiotherapy. We report a unique case of a 33-year-old man with a large intraventricular central neurocytoma. The characteristic histopathologic picture, the immunoreactivity for both synaptophysin and neuron-specific enolase, and the ultrastructural features of neuronal differentiation distinguished it from ependymoma and oligodendroglioma. The mitotic activity (up to 3 mitoses/10 high power field) and the high percentage of Ki-67-staining tumor cells (labeling index, 5.0%) in our case were consistent with the atypical variant of central neurocytoma. The patient underwent craniotomy and partial resection of the tumor. Unfortunately, he died of hydrocephalus and brain edema, the next day.