Clear Cell Ependymoma

Suh, Jae Hee; Hong, Seung Mo; Lee, In Chul

Abstract

The clear cell variant of ependymoma is a rare, recently described, intracranial tumor which is composed of clear neoplastic ependymal cells. Clear cell ependymomas may share characteristic histologic features of oligodendrogliomas or central neurocytomas; striking nuclear uniformity, perinuclear halos, and numerous angulated capillaries. In contrast to oligodendrogliomas, however, clear cell ependymomas are noninfiltrating tumors with sharp boundaries. Perivascular pseudorosette formation is frequent. Oligodendrogliomas are usually nonreactive for GFAP compared to diffuse immunoreactivity of clear cell ependymoma. Central neurocytomas may also be differentiated by their immunoreactivity for synaptophysin. This is a case of clear cell ependymoma in a 40-year-old man. By computed tomography and magnetic resonance imaging scans, a well circumscribed cystic tumor with mural nodule was demonstrated in the right frontal lobe. It was 6cm in diameter and well enhanced. Histologically, it was sharply demarcated from the brain parenchyma. The cystic wall was lined by atypical ependymal cells, which "transformed" to clear cells in the solid area. The cells had uniform nuclei and perinuclear halos. Mitotic figures and necrotic foci were focally present. The cells were immunoreactive for glial fibrillary acidic protein (GFAP), while synaptophysin was negative. Electron microscopy revealed densely packed polyheadral cells with scant organelles and well developed intercellular junctions.