Malignant Transformation of a Rosette-Forming Glioneuronal Tumor to Glioblastoma

Background A rosette-forming glioneuronal tumor (RGNT), a rare brain tumor, presents as a benign feature with a favorable outcome. To date, a few cases with aggressive behaviors, such as recurrence or dissemination, but none with malignant transformation, have been reported. We describe 1 case that recurred as glioblastoma after complete resection of the benign RGNT. Case Description A man aged 58 years presented with headache and dizziness without neurologic symptoms. Magnetic resonance imaging showed a 4 × 2.5 cm, well-demarcated mass in the left cerebellar hemisphere. The patient underwent gross total resection of the tumor and a diagnosis of RGNT was made. There was no evidence of recurrence on serial follow-up. However, a recurrent heterogeneous enhancing mass in the previous surgical cavity was observed on a 7-year postoperative magnetic resonance imaging scan. Reoperation was performed and a histopathological study revealed a glioblastoma. Conclusions To the best of our knowledge, this is the first case of spontaneous malignant transformation of an RGNT. Our case may be helpful in better understanding the biological behavior and clinical outcome of RGNT. We emphasize the malignant potential of this rare tumor and the necessity of future large-scaled research for most appropriate therapeutic strategies.