Nonteratoid medulloepithelioma of the retina with electron microscopic and immunohistochemical characterization.

Medulloepitheliomas are rare intraocular tumors, predominant in children, and originate mainly from undifferentiated nonpigmented epithelium of the ciliary body. These tumors rarely involve the optic nerve or the retina. They are classified as nonteratoid and teratoid types; the latter contains heterologous tissues. The teratoid variant of medulloepitheliomas involving the optic nerve or the retina is reported in four patients only. We describe the first case of a benign nonteratoid medulloepithelioma of the retina in a 3 1/2-year-old girl with immunohistochemical and electron microscopic characterization.