Radiation-induced meningiomas in multiple regions, showing rapid recurrence and a high MIB 1 labeling index: a case report and review of the literature.

Combined chemotherapy and prophylactic cranial irradiation has improved the prognosis of children with acute leukemia. However cranial irradiation carries a latent risk of the induction of secondary intracranial tumors. We encountered a patient who developed multiple intracranial radiation-induced meningiomas (RIMs) 25 years after prophylactic cranial irradiation for the treatment of acute leukemia in childhood. The patient had 3 intracranial lesions, 1 of which showed rapid growth within 6 months; another of the tumors also enlarged within a short period. All of the tumors were surgically treated, and immunohistochemistry indicated a high MIB-1 labeling index in each of the multiple lesions. In the literature, the MIB-1 labeling indices of 27 tumors from 21 patients were examined. Among them, 12 recurrent tumors showed higher MIB-1 labeling indices compared to the MIB-1 labeling indices of the non-recurrent tumors. Overall, 11 of the patients with RIM had multiple lesions and 8 cases developed recurrence (72.7%). RIM cases with multiple lesions had higher MIB-1 labeling indices compared to the MIB-1 labeling indices of cases with single lesions. Collectively, these data showed that the MIB-1 labeling index is as important for predicting RIM recurrences, as it is for predicting sporadic meningioma (SM) recurrences. RIMs should be treated more aggressively than SMs because of their greater malignant potential.