Congenital adenoma of the iris and ciliary body: light and electron microscopic observations.

A 23-year-old man had a lesion in the right inferior iris which appeared to have enlarged since it was first seen when the patient was aged 5 years. The lesion was excised by a partial iridocyclectomy. Histopathologically the neoplasm was composed of both pigmented and non-pigmented cells. Pseudoacini, containing acid mucopolysaccharides, were present throughout the tumour matrix. Electron microscopically the non-pigmented cells were found to possess a convoluted plasmalemma, abundant rough endoplasmic reticulum, and numerous desmosomes and gap junctions. The pigmented cells contained large, round, mature melanosomes, occasional premelanosomes, and desmosomes, which resembled the posterior pigment epithelium of the iris. The intercellular matrix contained fine collagen fibrils resembling vitreous. We believe that this neoplasm represents a congenital adenoma of the ciliary body and iris.