ROSETTE-FORMING GLIONEURONAL TUMOR: REPORT OF A CHIASMAL-OPTIC NERVE EXAMPLE IN NEUROFIBROMATOSIS TYPE 1: SPECIAL PATHOLOGY REPORT

OBJECTIVE: Rosette-forming glioneuronal tumor is a rare, rather recently described tumor featuring a highly distinctive, biphasic histological pattern, including a cytologically uniform neuronal component of Homer-Wright type pseudorosettes and an accompanying astrocytic element resembling pilocytic astrocytoma. Its occurrence in the posterior fossa and association with the fourth ventricle is stereotypical and a feature of all reported cases. CLINICAL PRESENTATION: In this article, we describe the first rosette-forming glioneuronal tumor arising out-side this site, a histologically classic example involving the anterior visual pathway and associated with neurofibromatosis type 1. INTERVENTION: Genetic (fluorescent in situ hybridization) studies demonstrated no large deletion in either normal or neoplastic tissue, indicating that the genetic abnormality underlying neurofibromatosis type I in this patient is likely a very small deletion or point mutation. CONCLUSION: The relation of the tumor to the underlying neurofibromatosis type 1 cannot be assessed.