Supratentorial extraventricular WHO grade III (anaplastic) ependymoma 17 years after total removal of WHO grade II ependymoma of the fourth ventricle.

We report a WHO grade III ependymoma of the supratentorial interhemispheric fissure and grew to form a large mass with anaplastic transformation without local recurrence 17 years after the total removal of a fourth ventricular WHO grade II ependymoma. We emphasize the necessity of long-term follow-up, even in benign ependymomas.