The significance of atypical mitoses in malignant meningiomas.

A group of 5 selected malignant meningiomas was studied in relation to the incidence and morphology of the mitoses. Beside a high mitotic rate many structural chromosomal abnormalities were observed. In agreement with other malignant onco-types previously studied, the authors suggest that atypical mitoses together with a tissue and cytological undifferentiation may be assumed to be an important prognostic criterium for meningiomas. The problem of malignancy in meningiomas has not been, so far, satisfactorily resolved, so that, in our opinion, the definition of even minimal details may be of some interest. For example, as it clearly appears from reviewing the literature on this sugject, no particular attention has been paid to the mitotic features. Referring to previous studies on the mitotic abnormalities in different malignant cerebral onco-types, the authors aimed to examine the various mitotic aspects in a limited group of tumors selected on the basis of clinical and histological malignancy.