Primitive neuroectodermal tumor of the orbit in a 5-year-old girl with microphthalmia

Purpose: To report an orbital, intraconal, primitive neuroectodermal tumor (PNET) in a 5-year-old child with microphthalmia since birth. Methods: Orbitotomy was performed and a large, polycystic, retroscleral, intraconal tumor was removed and subsequent histological, immunohistochemical and electron-microscopic analyses of the excised mass were performed. Results: The tumor showed characteristic features of peripheral primitive neuroectodermal tumor including pseudorosettes, positive immunohistochemical reactions for the MIC2 gene and synaptophysin and ultrastructural finding of neurosecretory granules. Conclusion: This case is the first reported intraconal PNET of the orbit, and the first orbital case that expresses the MIC2 gene. In spite of the aggressive malignant features of peripheral PNET, the orbital variety seems to be the least aggressive since most of the reported patients are still alive.