Radiation-induced tumours of meninges. Report on eight cases and review of the literature.

BACKGROUND AND PURPOSE: Despite their rarity, post-radiation meningeal tumours seem to be a growing problem due to the increasing application of radiation therapy. The aim of the study was to ascertain the specific features of these tumours.

MATERIAL AND METHODS: Among 433 intracranial meningeal tumours treated from 2000 to 2008, eight cases (2%) have been presumed to be associated with high-dose therapeutic radiation for previous neoplasm of the head (7) or neck (1). On average, tumours were diagnosed 24 years after irradiation. All patients had a solitary meningeal tumour, but two of them also developed other neoplasms in the irradiated area.

RESULTS: All tumours were microsurgically removed. The post-operative course was uncomplicated in two cases only. In the remaining 6 (75%), complications included liquorrhoea (2), brain oedema (1), venous thrombosis (1), bleeding into the tumour bed (1) and focal deficit due to manipulation (3). Most tumours (5) were WHO grade I meningiomas. These benign meningiomas exhibited some peculiar histological features, including focal increase of cellularity, focal enhancement of proliferation index, pleomorphism of nuclei, occasional mitotic figures and, in one case, evidence of brain invasion. One meningioma was assigned to WHO grade II, one to WHO grade III and one appeared to be meningeal fibrosarcoma. The event-free survival and overall survival rate at 4.4 years of follow-up were 63% and 75%, respectively.

CONCLUSIONS: Radiation-induced tumours of the meninges show certain characteristic histopathological features, which may promote invasiveness of the tumour and higher risk of malignancy.