Hamartomatous adenoma of the nonpigmented ciliary epithelium arising in iris-ciliary body coloboma. Light and electron microscopic observations.

A 2 1/2-year-old boy had a slowly enlarging mass at the site of a typical iris-ciliary body coloboma for 2 years. The mass was excised partially by iridocyclectomy. By light microscopy, the tumor cells were embedded in a rich mucoid stroma that contained abundant hyaluronidase-sensitive acid mucopolysaccharides. By electron microscopy the tumor showed light and dark cells with interdigitating cell membranes, desmosomes, gap junctions, multilaminar basement membrane, and numerous extracellular collagen fibrils that resembled vitreous fibrils. We believe that the tumor represents a hamartomatous (congenital) adenoma of the nonpigmented ciliary epithelium rather than a conventional (acquired) adenoma, since it developed precisely within a colobomatous defect of the iris and ciliary body.