Radiation-Induced Supratentorial High-Grade Glioma Following Medulloblastoma in the Right Cerebellar Hemisphere: A Case Report

Medulloblastoma is the most common malignant embryonal tumor of the central nervous system in the pediatric population, although it may also occur in adults. Its management requires a multimodal approach including surgical resection, craniospinal radiotherapy, and chemotherapy, which have significantly improved overall survival. However, these treatments are associated with late complications, among which radiation-induced secondary neoplasms are particularly relevant. We present the case of a 60-year-old male with a history of infratentorial medulloblastoma treated in 2020 with surgical resection, radiotherapy, and chemotherapy, who remained under active surveillance. Four years later, contrast-enhanced magnetic resonance imaging with spectroscopy revealed a new supratentorial lesion involving the genu of the corpus callosum, suggestive of a high-grade glioma. The patient underwent a right pre- and post-coronal craniotomy, where a poorly defined, grayish, avascular lesion was identified and biopsied. Histopathological and immunohistochemical analyses confirmed a high-grade glioma of glial origin, distinct from the initial medulloblastoma, supporting the diagnosis of a radiation-induced secondary neoplasm. Although meningiomas are the most frequently reported secondary tumors following craniospinal irradiation, high-grade gliomas represent a rare but aggressive complication with significant prognostic implications. This case underscores the importance of long-term imaging follow-up in patients treated with radiotherapy and highlights the need for further research to better understand the mechanisms underlying radiation-induced tumorigenesis.