[Importance of meningioma. Clinico-epidemiologic and histologic studies].

The clinical data and histological findings of 195 patients operated on because of meningiomas have been evaluated for the comparative epidemiological-morphological study of the biological validity of meningiomas under special consideration of the incidence of recidivation and malignant transformation. These were 127 women (65%) and 68 men (35%). The incidence peak of the tumour diseases for both sexes was found to lie between the 40th and the 59th year of age showing a frequency of 61 per cent. The assessment of the biological validity of meningiomas was based on the localisation, growth rate and recidivity of the tumours including histological criteria in the sense of the grading system after Zülch. The incidence of malignant meningiomas may amount to up to 10 per cent of the meningioma cases; the share in our own patients was 5.1 per cent. The incidence of recidivation of meningiomas was found to be 11.5 per cent after total tumour removal and 32 per cent after subtotal operation. The rate of the recurrence of meningiomas of the base was 52 per cent, thus being considerably higher than that of meningiomas of other localisations (3-28%). Malignant meningiomas show a particularly high recidivity. Among our own patients, there were ten cases of malignant meningiomas with 15 relapses (150%) while 185 benign meningiomas only showed a total of 30 relapses (16%). Invasive growth was found in the meningioma form classified histologically as malignant with 2.5 higher frequency than that of the benign forms of meningiomas. In recurrent tumours a malignant transformation of primary benign meningiomas was found. Malignant meningiomas with a formation of extraneural metastases are rare. Until now, only 72 cases have been reported in the literature.