Rosette-forming glioneuronal tumor: a pineal region case with IDH1 and IDH2 mutation analyses and literature review of 43 cases

Abstract

Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle is a mixed glio-neuronal neoplasm recently codified by the World Health Organization WHO Classification of Central Nervous System (CNS) Tumors (2007). To date, 43 cases have been described in the literature; most occurring in the fourth ventricle region. We report the fourth case involving the pineal region in a 16-year-old female with signs of increased intracranial pressure (ICP). A stereotactic biopsy of the mass was followed by a debulking procedure. Both specimens revealed classic RGNT histology. The patient had stable scans 7 months post-resection. The clinical, radiological and histopathologic features of the previously described 43 cases are reviewed along with our illustrative case. Mean age of patients was 30 ± 12.8 years with 1.9:1 female to male ratio. The most common presenting signs related to increased ICP and posterior fossa involvement, including: headache (62.8%), ataxia (39.5%) and vomiting and vertigo (both 16.3%). This tumor usually presents with cystic changes (54.5%) with focal enhancement (60.9%) and hydrocephalus (43.2%). Microcalcifications and satellite lesions were common radiographic observations. All reported cases had the classic biphasic pattern. Rosenthal fibers and eosinophilic granular bodies are each present in approximately two thirds of cases. Ki-67 labeling index is consistently low (mean (%): 1.8 ± 0.75 SD). The isocitrate dehydrogenase 1 or 2 mutation found in low grade diffuse gliomas is not identified in this RGNT case. Reported outcome is nearly uniformly excellent after complete or subtotal resection. A solitary report of recurrence after 10 years and the limited experience with this entity suggest that long term follow up is advisable.

Fig. 1

Preoperative MRI findings. a T1-weighted sagittal MRI shows a heterogenous predominantly isointense to slightly hypointense mass (arrow) centered in the pineal region and extending to the posterior aspect of the third ventricle. There is extensive associated mass effect, including upon the tectum, with effacement of the cerebral aqueduct. There is enlargement of the lateral and third ventricles due to obstructive hydrocephalus. Multiple hypointense foci within the tumor may indicate cystic areas. There is no extension of tumor to the fourth ventricle or cerebral aqueduct; b T1-weighted axial MRI with gadolinium shows no enhancement within the tumor

Fig. 2

Histologic features: a Low power microscopy reveals a biphasic tumor with neurocytic (right) and astrocytic (left) components, H&E, ×200; b Well-formed perivascular rosettes and true rosettes (inset), H&E, ×1,000; c Strong synaptophysin staining is noted among neurocytes and neurocytic cores, ×400; d High power view of the synaptophysin-positive neurocytic cores, ×1,000; e Glial fibrillary acidic protein immunostain highlights the piloid astrocytic component, ×200; and f Collections of oligodendrocyte-like cells are present, H&E, ×400

Fig. 3

Age distribution of rosette-forming glioneuronal tumor cases showing predominantly younger age group (11–40 age bracket). The mean age at presentation is 30.3 ± 12.8 years with 1.9:1 female to male ratio