Rosette-forming glioneuronal tumor (RGNT) is a rare brain tumor found almost exclusively within the fourth ventricle. These grade I tumors were first included in the World Health Organization (WHO) Classification for the central nervous system in 20071. Since then, approximately 49 cases have been published.
There are no reported cases of RGNT within the third ventricle, although this tumor has also been described in the pineal region, the tectum and within the aqueduct. Supratentorial localization is quite rare, with only three published: one was found in the septum pellucidum, another within the optic nerve in neurofibromatosis type 1 (NF1) patient and one in a patient with multiple RGNT in the lateral ventricle. The authors report the first case series in the literature of RGNT occurring within the posterior third ventricle.