Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 2, 2011, pp. 276-280

Neurology India, Vol. 59, No. 2, March-April, 2011, pp. 276-280

Case Report

Rosette-forming glioneuronal tumors: A report of two cases

Pankaj Sharma¹, Meenakshi Swain², Michelle De Padua², Alok Ranjan¹, Rahul Lath¹

¹ Department of Neurosurgery, Apollo Health City, Hyderabad, India
² Department of Pathology, Apollo Health City, Hyderabad, India

Correspondence Address: Rahul Lath, Department of Neurosurgery, Apollo Health City, Hyderabad - 500 033, India, rahullath@hotmail.com

Date of Submission: 08-Jul-2010
Date of Decision: 12-Jul-2010
Date of Acceptance: 07-Aug-2010

Code Number: ni11074

PMID: 21483133

DOI: 10.4103/0028-3886.79148

Abstract

Keywords: Glioneuronal tumor, rosette-forming, midbrain and suprasellar location

Introduction

Rosette-forming glioneuronal tumor (RGNT), initially described as dysembryoplastic neuroepithelial tumor (DNET) of the cerebellum, was considered as a separate entity based on distinctive morphology, location, age distribution and biologic behavior. ^[1] About 45 cases have been reported so far, and recently there has been a suggestion to label them as infratentorial or posterior fossa glioneuronal tumors. ^[2],[3],[4] This tumor predominantly affects young adults; typically arises in the midline; involves the cerebellum, wall or floor of the fourth ventricle and/or cerebral aqueduct; and may show parenchymal extension. ^[5],[6] We describe 2 cases of RGNT, one in the midbrain and one in a suprasellar location, and review the literature.

Case Reports

Case 1

A 16-year-old girl presented with complaints of diplopia and headache for the past 4 years. She was evaluated elsewhere and was started on antitubercular therapy (ATT) for a brainstem lesion suspected to be of tuberculous pathology based on radiological findings. During her follow up period, repeated scans showed no response to ATT, instead increase in size of the lesion was noted. At presentation to us, she had no neurological deficits. Gaze and eye movements were normal. Magnetic resonance imaging (MRI) scan of the brain showed a well-defined mass in the tectal region of the midbrain, which was hypointense on T1-weighted image, hyperintense on T2-weighted image, and showed no enhancement on contrast images [Figure - 1]. Fluid attenuated inversion recovery (FLAIR) image did not show significant perilesional edema. A computed tomography (CT) guided stereotactic biopsy was done via a transfrontal route. Histopathological examination showed tumor was biphasic, composed of sheets of moderately cellular astroglial proliferation with oval and spindled nuclei. The stroma was loose, and myxoid and microcystic changes were evident. At places the cells had piloid processes. Cells with small, round, regular nuclei with speckled chromatin were seen arranged as perivascular pseudo-rosette and true rosettes with central fibrillary matrix [Figure - 2]a. Foci of cells resembling oligodendroglial cells were seen [Figure - 2]b. There was no evidence of necrosis or mitotic figures. Immunohistochemistry with glial fibrillary acidic protein (GFAP) and synaptophysin was positive [Figure - 2]c, while the molecular immunology Borstel number one (MIB-1) index was low (<1%). The features were consistent with those of a rosette-forming glioneuronal tumor. Postoperatively she received 57 Gy of intensity-modulated radiation therapy in 27 cycles. At the last follow-up, 6 months later, she was asymptomatic.

Case 2

A 17-year-old boy presented with history of sudden loss of consciousness of few hours' duration and past history of headache for 1 year. On admission he was obtunded with a Glasgow Coma Score (GCS)of E1V2M5 (8/15). There were no focal neurological deficits. Initial CT scan of the brain showed a hyperdense lesion in the suprasellar and interpeduncular cistern with extension into the third ventricle and dilation of both lateral ventricles [Figure - 3]a. MRI was done, which showed a suprasellar mass involving the hypothalamus and extending into the third ventricle with hydrocephalus [Figure - 3]b. He underwent bilateral ventriculo-peritoneal shunt as an emergency procedure in view of his sensorium and bradycardia. Post procedure, he was symptomatically better and his sensorium improved. During further hospital stay, features of hypothalamic dysfunction were noticed as hyponatremia with high output, and a fluctuating level of sensorium was observed. Hormonal analysis showed low level of cortisol, and he received steroid replacement therapy. Right fronto-temporal craniotomy was done, and grayish vascular suckable tumor in the third ventricle was biopsied. The tumor showed area of diffuse astroglial proliferation with oval nuclei and fibrillary cytoplasm. Also seen were cells with small, round and regular nuclei with stippled chromatin arranged in a neurocytic rosette around delicate neuropil matrix [Figure - 4]a and [Figure - 4]b. There was no evidence of necrosis, mitotic figure or endothelial proliferation. Immunohistochemistry with GFAP and synaptophysin was positive [Figure - 4]c. MIB-1 index was low (<1%). Biopsy report was consistent with a diagnosis of rosette-forming glioneuronal tumor. The patient is under regular radiological and clinical follow-up and is asymptomatic. The residual tumor is small and is being followed up with serial imaging.

Discussion

Rosette-forming glioneuronal tumor (RGNT) is a recently classified central nervous system tumor corresponding to WHO grade I and shares the new international classification of diseases for oncology (ICD-O) code 9509/1 with the papillary glioneuronal tumor (PGNT). ^[5],[6] Two large series, one by Komori et al. in 2002 ^[1] (11 patients) and the other by Shah et al. in 2009 ^[3] (6 patients), have been reported. To date, a total of 45 cases have been reported in the English literature [Table - 1]. ^{[1],[2],[3],[4],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21]} RGNT is a slow-growing tumor of the fourth ventricular region. Its population-based incidence is unknown, and this tumor predominantly affects young adults with a mean age of 29.2 years, with the youngest being 6 years old; and the oldest, 59 years of age. ^[3] There is a female preponderance (female-to-male ratio, slightly more than 2:1). ^[2],[3],[4] It has not been described in a familial form; however, a case of RGNT in a neurofibromatosis type-1 patient was reported but no genetic link was identified. ^[7] It has also been recently described in a patient with dysgenetic tricho-rhinopharyngeal type I syndrome. ^[8] The most common presenting manifestations are headache and ataxia, followed by visual disturbances and vertigo. ^[6] Other features of posterior fossa lesions are also present. As described initially, they are midline lesions centered in the fourth ventricle; however, tumors primarily situated in the surrounding tectal/ pineal and aqueductal regions are also well documented. Multifocal lesions with fourth ventricular, vermian, dorsal pontine, mesencephalic and thalamic components have also been reported. ^[5],[6] The occurrence of RGNT outside of the posterior fossa is rare and includes the suprasellar region and spinal cord [Table - 1].

On CT scans, the lesions are midline, relatively well circumscribed, solid, cystic or mixed and usually enhance focally with contrast. ^[1],[6] MRI features are T1-isointensity/ hypointensity and T2-hyperintensity with no contrast enhancement. ^[1],[5],[6] Intratumoral hemorrhage, like what was seen in our second case, is rare and has been previously described in two other reports. ^[9],[10]

Histopathology shows 2 types of tissue. The first is a bland perivascular astroglial proliferation with spindle and piloid cells resembling pilocytic astrocytoma. The second component is composed of cells with small and regular nuclei and speckled chromatin forming perivascular pseudo-rosettes and miniature neurocytic rosettes with a delicate neuropil matrix. Significant cytologic atypia and mitotic activity are absent. On immunostaining, synaptophysin labels the neuropil matrix and perivascular pseudo-rosettes. ^[1],[5],[6] The astrocytic component is labeled by GFAP and S-100. ^[1],[6] MIB-1 proliferation index is typically low (ranging from 0.35% to 3.07%). ^[1],[6] The nature of the tumor is indolent, as evidenced by absence of aggressive histologic features and low MIB-1 proliferative index. ^[1] Although RGNTs are benign tumors with the possibility of surgical cure and favorable prognosis, their location complicates surgical removal and imparts a significant risk of neurologic injury. ^[6] A survey of 45 cases with follow-up (range, 2-84 months; mean, 22 months) reveals no instance of tumor regrowth when treated by gross total resection alone. One case of recurrence after 10 years of follow-up ^[11] and one death have been reported. ^[1]

One patient in the series by Komori et al. and 1 patient of ours received postoperative radiation. ^[1] We considered radiation in our first case as there was documented increase in the size of the lesion. Radical resection is best avoided because of the anatomic location of these tumors. Significant postoperative morbidity, particularly affecting multiple cranial nerves, is common after major surgical resection. Long-term follow-up and more case reports are required to form uniform guidelines. Extra-fourth-ventricular locations, although rare, are being increasingly reported, like in our 2 cases.

References

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