AB051. Multiple meningiomas developed outside the radiation field after cranial irradiation: a case report.

ABSTRACT

BACKGROUND: Cranial irradiation has well-known long-term side effects, including radiation-induced neoplasms and vasculopathy. This report describes a case of aggressive and rapid-growing multiple meningiomas developed outside the radiation field after the treatment of medulloblastoma. CASE DESCRIPTION A 6-year-old boy underwent surgery (gross total resection) and radiotherapy (19.8 Gy for posterior fossa only) against medulloblastoma in the 4th ventricle. The patient could not receive further craniospinal irradiation because of ventriculoperitoneal shunt-related complications. Eighteen years after the radiotherapy, the first meningioma developed in the right temporal convexity, without recurrence of medulloblastoma. It was left untreated because it was asymptomatic. Three years later, the meningioma grew from 0.6 to 6.3 cm3 in volume and another large meningioma (22.1 cm3) developed in the left temporal convexity with additional small meningioma in the right frontal convexity. The left large temporal meningioma showed aggressive nature invading the adjacent temporal bone and temporalis muscle. It was completely resected and the histology revealed as transitional meningioma with 2% of Ki-67. Another new meningioma was identified on the right cerebellar convexity three years post-craniotomy. Subsequent follow-up indicated a progressive increase in the tumor size and gamma knife radiosurgery was performed with right frontal convexity small meningioma. The patient is currently under ongoing surveillance through follow-up assessments. CONCLUSIONS: For patients who received radiotherapy at a young age, clinicians should consider the possibility of secondary neoplasm development even outside the radiation field. Careful imaging follow-up and surgical management are warranted because of the aggressive nature of secondary tumors even though benign in histology.