Rosette-Forming Glioneuronal Tumor Originating From the Spinal Cord: Report of 2 Cases and Literature Review.

Rosette-forming glioneuronal tumor (RGNT) is a recently recognized and rarely encountered tumor occurring in the fourth ventricle. RGNT was first described as a new entity for the distinct clinicopathologic features by Komori et.al. in 2002. Histologically, it is composed of 2 distinct features: a glial component, resembling pilocytic astrocytoma, and a neurocytic component forming neurocytic rosettes and/or perivascular rosettes. We report 2 extremely rare cases of RGNT arising from the spinal cord, which were misdiagnosed as ependymoma and astrocytoma preoperatively. Symptoms included dissociated sensory disturbances and episodic pain and fatigue of 2 years' duration in case 1, as well as motor disturbance for 2 months' duration in case 2. Magnetic resonance imaging (MRI) revealed these masses in the thoracolumbar (T7-L1) and cervicothoracic (C3-C7) spinal cord. The solid component appeared hypointense in T1-weighted MRI sequences, hyperintense in the T2-weighted MRI sequences, and heterogeneous in MRI images enhanced with gadolinium contrast medium in both cases. Gross total resection was performed via a median laminectomy. Postoperative pathological examination confirmed the diagnosis of RGNT. In addition, extensive analysis of genetic mutations was performed to explore the relationship with glioma, including telomerase reverse transcriptase promoter, isocitrate dehydrogenase 1/2, BRAF-V600E, and O(6)-methylguanine-DNA methyltransferase promoter. No radiotherapy or chemotherapy were performed in these two cases. As of the latest follow-up, both patients had a good prognosis. Given the widely varying clinical characteristics of, prognosis of, and treatments for spinal tumors, differential diagnosis is of great importance before surgery. Consideration of the tumor location and the patient's age and sex, in combination with the imaging features, may be the best approach to narrowing the differential diagnosis. Surgery is the preferred treatment for RGNT. We do not recommend to implement adjuvant radiotherapy and chemotherapy in these patients except the invasive or recurrent tumors. Further examination and routine follow-up should be recommended to estimate the long-term prognosis.