Supratentorial lobar pilocytic astrocytomas: report of 45 operated cases, including 9 recurrences.

45 cases with supratentorial, lobar--mainly temporo-parietal--pilocytic astrocytoma are analysed. The mostly highly vascularized tumours frequently present with histologically different tissue components. Formation of cysts of various size was found in 67%. The tumour usually ran a benign clinical course with a comparatively low incidence of recurrence. Malignant transformation of recurrent tumours was not observed. Radiotherapy of conventional dosage did not prove to have any influence on survival, neither post-operatively nor after re-operation. Transformation of persisting pluripotential cells of the subependymal periventricular plate after migration to the surface of the brain is being discussed as the origin of this variant of pilocytic astrocytoma.