Intracranial germinomas are considered one of the most radiosensitive tumors and 
are curable by radiotherapy alone. Although patients can expect long-term 
survival, the adverse effects of radiotherapy and late sequelae in survivors are 
a major concern. Radiation-induced secondary neoplasms are one of those sequelae 
and are a serious concern because they are often connected directly with life 
prognosis. We describe a case of radiation-induced glioblastoma after 
radiotherapy for germinoma. An 11-year-old boy with basal ganglia germinoma was 
successfully treated with postoperative cranial irradiation. At the age of 40 
years, he was admitted to our hospital for aphasia and memory disturbance. CT 
and MRI revealed a tumor in the left parietal lobe with dissemination. The tumor 
of the parietal lobe was removed surgically, and pathohistologically, it was 
diagnosed as glioblastoma. Long-term survivors who receive radiotherapy for 
germinomas in childhood are at risk for late complications, including 
radiation-induced neoplasms. Therefore, careful follow-up neurological 
examinations are recommended in these patients, even 20-30 years after 
radiotherapy.