Rosette-forming glioneuronal tumour of the fourth ventricle: case report and review of the literature.

Rosette-forming glioneuronal tumour (RGNT) of the fourth ventricle is one of the newly described primary tumours of the central nervous system. These tumours have two components of both neurocytic and glial areas but usually the glial component of the tumour predominates. They have biphasic cytoarchitecture with two elements; neurocytic rosettes resembling Homer-Wright rosettes, and astrocytic component resembling a pilocytic astrocytoma. They are low-grade tumours with lack of histopathological signs of malignancy. Here, clinical, magnetic resonance, computed tomography (CT) and pathological features of rosette-forming glioneuronal tumour of posterior fossa are presented. A 29-year-man was admitted with an acute neurological deterioration. A three ventricular hydrocephalus and a hypo-density around vermis in the posterior fossa were seen in his CT scans. He did well after an emergency external ventricular drainage. He had an elective operation and a mass that was reported to be a rosette-forming glioneuronal tumour of the fourth ventricle was excised.