Choroidal epithelial cyst. Case report.

A supratentorial cyst in the leptomeninges of an 8-month-old infant was studied with the electron microscope. The lining of the cyst consisted of a single layer of peg-shaped epithelial cells rich in organelles and glycogen. Their free border had numerous microvilli but no cilia, and their basal portions rested on a basement membrane. Tight junctions and interdigitations were frequent between contiguous cells. The blood vessels were fenestrated. Since these features characterize developing choroidal epithelial cells, we felt the diagnosis of choroidal epithelial cyst was justified. Cysts lined by choroidal epithelium may continue to secrete cerebrospinal fluid after surgical extirpation when this is incomplete. Accumulation of the fluid in the partially excised cyst bed may therefore account for recurrence of symptoms.