A Multifocal Glioneuronal Tumor with RGNT-Like Morphology Occupying the Supratentorial Ventricular System and Infiltrating the Brain Parenchyma.

BACKGROUND: Rosette-forming glioneuronal tumors (RGNTs) with multifocal growth throughout the ventricular system are extremely rare, and only 1 case of RGNT with dissemination limited to supratentorial ventricles has previously been reported. Recent evidence based on molecular data suggest that low-grade glioneuronal tumors (GNT) involving the septum pellucidum and the lateral ventricles, with either dysembryoplastic neuroepithelial tumor-like or RGNT-like features, may belong to a neuropathologic entity distinct from cortical dysembryoplastic neuroepithelial tumor and "typical" fourth ventricle RGNT, respectively. Given their rarity, the classification of these neoplasms is still uncertain and their clinicopathological and radiological aspects are only partially known. CASE DESCRIPTION: A 24-year-old male presented a GNT with RGNT-like morphological features centered in the septum pellucidum with multifocal masses occupying the lateral ventricles and the third ventricle with extraventricular infiltration of the frontal lobe. The patient underwent subtotal resection and 4 years follow-up. The clinicopathological and radiological features of the neoplasm are discussed. CONCLUSIONS: Advanced magnetic resonance imaging (magnetic resonance spectroscopy and perfusion-weighted imaging) may provide valuable information in the differential diagnosis between rare GNTs and other more frequent intraventricular neoplasms. In the present case, the enhancing remnant portion of the tumor showed remarkable contrast enhancement variability during the follow-up with slow in situ progression. However, available data suggest that spontaneous contrast enhancement "fluctuations" over time in RGNT may not represent a reliable indicator of tumor behavior.