Rosette-forming glioneuronal tumor: report of an unusual case with intraventricular dissemination.

A rosette-forming glioneuronal tumor (RGNT) was encountered in a 16-year-old Chinese girl. She experienced seizures with loss of consciousness for 1 month prior to diagnosis. A brain MRI revealed multifocal masses occupying all of the ventricular system associated with marked hydrocephalus. A biopsy was performed on the right lateral ventricle using a neuroendoscope and the patient was given postoperative radiotherapy. She was followed for 7 months, and there was no radiological or clinical evidence of tumor progression. Histological examination demonstrated two regions characterized by predominant neurocytic rosettes and scant low grade astrocytoma. No histological anaplasia was present. Immunohistological studies showed that the small round tumor cells forming rosettes were strongly positive for Olig2. A chromosome 1p/19q co-deletion was not detected by FISH analysis. While the pathological features of our case closely resembled those reported in the original description, the diffuse intraventricular growth pattern of the tumor was different from previous examples. Further long-term follow-up studies are required to assess the biological behavior and clinical outcome of the RGNT entity.