Secondary glioblastoma multiforme (sGBM) can occur after a long latency period 
following radiation treatment of various diseases including brain tumors, 
leukemia, and more benign disorders like tinea capitis. Outcomes of 
radiation-induced sGBM remain poor in both children and adults. We report a case 
of a 16-year-old girl with a history of disseminated juvenile pilocytic 
astrocytoma treated with chemotherapy and craniospinal radiation 9 years prior 
who developed sGBM in the absence of a tumor predisposition syndrome. She 
presented with a several-week history of headaches and no acute findings on 
computed tomography compared to baseline neuroimaging 3 months prior. Repeat 
computed tomography performed just 3 weeks later for worsening headaches 
revealed a new large posterior fossa tumor where pathology confirmed the 
diagnosis of sGBM. In spite of maximal surgical resection, reirradiation, and 
adjuvant chemotherapy, she died 1 year postdiagnosis. Our case highlights the 
potential late effects of high-dose cranial radiation, how symptomatology may 
precede neuroimaging findings, and the rapid formation of sGBM that mirrors that 
of de novo Glioblastoma Multiforme.