Early Neuroblastic and Astrocytic Differentiation Demonstrated Immunohistochemically in a Small Intraocular Medulloepithelioma.

ABSTRACT

PURPOSE: To investigate the source of fibrous astrocytes and neuroblasts in a small ciliary body medulloepithelioma appearing as a leukocoria in a 3-week-old baby girl. METHODS: Histopathologic and immunohistochemical studies included Alcian blue, periodic acid-Schiff, and antisera for the detection of S100 protein, CD99, glial fibrillary acidic protein (GFAP), CRX, NeuN, neurofilaments, synaptophysin, desmin, and myogenin. RESULTS: A small, nonteratoid ciliary body medulloepithelioma with collections of Alcian blue+ mucoplysaccharides was present in the enucleated globe. The retinal mass displayed multilaminar dysplastic rosettes that were CRX+, NeuN-, and synaptophysin-. Intraretinal neurofilaments and scattered NeuN+ neurocytes were also identified. At the base of the retinal mass ribbons and pseudopapillae of CRX+, NeuN- medullary epithelium were found. The latter developed from an S100+ and weakly CD99+ monolayer of premedullary epithelium. GFAP+ fibrous astrocytes and NeuN- neuroblasts streamed from the medullary epithelium. CONCLUSIONS: A multilaminar medullary epithelium and a precursor monolayer of premedullary epithelium were both identified. Neuroblasts and fibrous astrocytes were determined to arise separately from the medullary epithelium. The early stage of tumorigenesis afforded by a small tumor provided the opportunity to discover morphologic and immunohistochemical evidence for these differentiations.