Supratentorial subarachnoid epithelial cyst: case report and ultrastructural study.

Supratentorial epithelial cysts are rare entities that have evoked controversy regarding their pathogenesis. Recent ultrastructural studies have failed to resolve this controversy. We present a case report and an ultrastructural study of such a cyst. The cyst wall was lined by columnar epithelial cells with prominent cilia and microvilli at their apical surface. They were joined by well-developed junctional complexes and contained abundant intracytoplasmic, electron-dense, granular material, some of which was membrane-bound. These ultrastructural findings suggest that epithelial cysts are derived from elements of the embryological tela choroidea.