Adult type of medullo-epithelioma of the ciliary body.

Three different types of tumors are known to develop from the pars ciliaris reti­ nae: the benign Fuchs epithelioma, the ma­ lignant medullo-epithelioma of the embry­ onic type, and the malignant medullo-epi­ thelioma of the adult type. Chart 1 indicates the relationship of these tumors to the prim­ itive retinal elements and to the tumors of other parts of the retina. The Fuchs epithelioma simply represents an epithelial hyperplasia which often occurs in senile eyes or in cases of chronic inflam­ mation. It is of some interest for this study since some authors believe that the adult type of medullo-epithelioma of the ciliary body develops after chronic irritation from such hyperplastic epithelium. The medullo-epitheliomas of the embryonic type (dik-tyoma) originate in the internal, nonpig-mented epithelium of the ciliary body; they usually occur in young children, are malig­ nant, but are not known to metastasize. Verhoeff 1 published an outstanding de­ scription of a tumor of this type and was first to find with special staining methods that the formations of this tumor repre­ sented different stages of the embryonic retina. He found embryonic rods and cones, radial fibers of Muller, astroglia, and parts of a primitive hyaloid membrane in this tumor. Verhoeff suggested calling the em­ bryonic type of medullo-epithelioma (dikty-oma) a "terato-neuroma" since it typically exhibits elements which resemble those of the primitive retina and since the tumor is highly differentiated. The embryonic type of medullo-epitheli-oma (diktyoma) is considered to be com­ posed of more primitive cells while the adult type (also called malignant epithelioma) ex­ hibits cells of a later stage of development of the ciliary epithelium. The medullo-epi-theliomas of the adult type also originate in the nonpigmented ciliary epithelium without, however, being known to imitate the embry­ onic retina. The adult type of medullo-epi­ thelioma is described as being composed of single layers of cells which closely resemble the adult ciliary epithelium. This type of medullo-epithelioma occurs typically in blind, phthisical eyes of adult persons. It is also malignant and« is not known to metasta­ size. Fuchs 2 published an extensive discussion of the benign and malignant tumors of the pars ciliaris retinae. He accepted Verhoeff's conception of the embryonic type of me­ dullo-epithelioma but not the name which Verhoeff suggested. Fuchs pointed out that both types of medullo-epitheliomas, the em­ bryonic and the adult type, are closely re­ lated. This close relationship was later again emphasized …