Malignant transformation in pediatric spinal intramedullary tumors: case-based update.

BACKGROUND: In children, intramedullary spinal cord neoplasms are rare. These are typically low-grade neuroepithelial tumors, most commonly astrocytomas, ependymomas, and gangliogliomas. Malignant transformation, while common in recurrent adult low-grade gliomas, is an unusual event in pediatric low-grade neoplasms, specifically in intramedullary spinal cord tumors. ILLUSTRATIVE CASES: We report two cases of malignant transformation in low-grade neuroepithelial tumors of the pediatric intramedullary spinal cord. Two children with intramedullary tumors, one with a WHO grade I ganglioglioma and one with a low-grade astrocytoma, were treated surgically, diagnosed histologically, and followed through the course of their disease. Both patients' tumors transformed to higher grades without prior irradiation or chemotherapy, and without a genetic predisposition to tumorigenesis. DISCUSSION: Malignant transformation can occur in low-grade intramedullary neoplasms in children. This is a novel documented event for pediatric intramedullary spinal cord tumors and a rare event for all pediatric low-grade neuroepithelial tumors without induction by irradiation. A survey of the relevant literature reveals an underwhelming number of studies focusing on malignant transformation in children's CNS tumors relative to adults. Further investigation into molecular mechanisms of pediatric low-grade neoplasms may reveal more aggressive tumor sub-variants predisposed to malignant degeneration.