Intraventricular meningioma with anaplastic transformation and metastasis via the cerebrospinal fluid.

We report a surgical case of intraventricular meningioma that arose in the trigone of the right lateral ventricle of a 61-year-old woman. Local recurrence and metastasis (dissemination) via the CSF to the fourth ventricle developed about 52 months postoperatively. Further subarachnoid dissemination in the pontine base and spinal cord occurred 6 months later. The tumor exhibited a histopathological appearance of transitional meningioma without cellular atypism in the original specimen, but in the metastatic nodules in the fourth ventricle and spinal subarachnoid space the histopathology was that of typical anaplastic meningioma. Only four cases of anaplastic intraventricular meningioma that developed metastasis via the CSF have been reported. This report presents the fifth case, which is also the second case in which progression from ordinary low-grade meningioma to anaplastic meningioma was demonstrated histopathologically.