Brain tumours are roughly divided into two categories: benign and malignant. Grade 2 WHO-rated astrocytomas, spongioblastomas and oligodendrogliomas, as well as tumours representing a mix thereof (oligoastrocytomas, etc.) belong to the former category, as does a special group of tumours containing astrocytomas of the thalamic – hypothalamic system and the chiasmatic – hypothalamic system. Grade 3 and 4 astrocytomas (Gliobalstomas) and gliosarcomas do not however belong to the benign tumour category. Ependymomas, ependymoblastomas and subependymomas are rated differently within the WHO classification. Non-brain resident tumours such as plexus papillomas or colloid cysts can lead to disturbances in cerebrospinal fluid circulation and brain pressure in the cerebral ventrical system. Tumours of the pineal region (pinealomas, pineocytomas, and pineoblastomas) can be treated radically and therefore curatively. Metastases, primary lymphomas and epidermoid cysts, can all look very much like a brain tumour. In some of the above cases, microsurgical resection, irrespective of the anatomical position or dignity of the tumour, is curative, in others however it may simply be life-prolonging or the first step prior to subsequent treatment (chemotherapy or radiotherapy).
The application of modern methods of tumour identification (staining of the tumour ALA) is a valuable tool in treatment optimisation.