Choroidal epithelial cyst of the prepontine region: case report and ultrastructural study.

A case of choroidal epithelial cyst of the prepontine region is reported. The cyst wall was studied using light and electron microscopy. Electron microscopy revealed that the lining of the cyst consisted of a single layer of epithelial cells resting on a basement membrane. The epithelial cells contained numerous club-shaped microvilli and occasional cilia. There were no coating materials on the surface of the microvilli. Tight junctions and interdigitations were present between contiguous cells. The blood vessels were fenestrated. These ultrastructural findings suggest that the epithelial cyst was derived from the choroidal epithelium rather than ependyma or endodermal tissue.