Rosette-forming Glioneuronal Tumor: Rare Case Presented with Spontaneous Disappearance of Contrast Enhancement.

This report presents rosette-forming glioneuronal tumor (RGNT) of the tectum in a 24-year-old woman in whom spontaneous disappearance of contrast enhancement (CE) on magnetic resonance (MR) imaging was observed during 9-year follow-up period before therapeutic intervention. MR imaging obtained 9 years ago when she first visited local hospital with headaches showed a mass of the brain stem with CE. Follow-up MR imaging showed disappearance of CE without tumor growth. Nine years later, she was admitted to our hospital with headache and nausea, due to obstructive hydrocephalus. She underwent endoscopic third ventriculostomy (ETV) and tumor biopsy. Histological study revealed RGNT. To our knowledge, this is the first report presenting that the RGNT may show spontaneous disappearance of CE without tumor growth. It is unclear what this phenomenon means, however, knowledge of this phenomenon may be helpful for correct diagnosis and for follow up of RGNT.