[Histopathology of glioma relapses].

The histological structure of gliomas and their relapses is an expression of the biological behaviour and thus permits certain prognostic statements. Especially astrocytomas show a tendency to progressive dedifferentiation. In oligodendrogliomas there is a slight tendency to dedifferentiation and in ependymomas it is very seldom. Recurrent pilocytic astrocytomas are without dedifferentiation in our material. The change in the histological features found in many gliomas on the examination of relapses is to be considered as an expression of changed biological activity.