A medulloepithelioma, or diktyoma, is a congenital tumor of the ciliary body. The prefix medullo- suggests that its origin is in the medullary epithelium, which not only lines the neural tube but also forms the primitive bilayered optic cup. Medulloepitheliomas can also arise from iris, optic nerve, or retina. They are congenital, unilateral tumors that display no evidence of genetic transmission. Affected children present with a loss of vision during the first decade of life with a mass in the ciliary body, glaucoma, or cataract. Medulloepitheliomas can be classified as teratoid or nonteratoid, with each type further divided into benign or malignant. They are, for the most part, slow-growing tumors that usually do not metastasize. In adults, medulloepitheliomas can be malignant.