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Rosette-forming glioneuronal tumor of the fourth ventricle--case report.

Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle is a rare tumor included as a novel glioneuronal neoplasm in the 2007 World Health Organization classification of brain tumors. A 15-year-old female patient presented with RGNT of the fourth ventricle manifesting as headache persisting for one month. Magnetic resonance imaging disclosed a nonenhanced solid mass in the fourth ventricle and vermis. The tumor was gross totally resected. Histological examination revealed biphasic neurocytic and glial architecture. The neurocytic component consisted of uniform neurocytes forming neurocytic rosettes and perivascular pseudorosettes. Only 31 cases of RGNT have been reported. RGNT of the fourth ventricle should be considered in the differential diagnosis of infratentorial lesions in young adults. The prognosis is benign, but relatively aggressive behaviors such as tumor growth, recurrence, and acute deterioration due to intratumoral hemorrhaging can occur. Surgical resection requires care to prevent major surgical morbidities associated with lesions invading the cerebellum or brainstem.