Neurological tumours are categorized by the WHO as follows: neuroepithelial tumours (gliomas, oligodendrogliomas, ependymomas, pineal parenchymal tumours, medulloblastoma, neuronal and neuroglial tumours); cranial and paraspinal nerve tumours (schwannoma, neurofibromas); meningeal tumours (meningiomas); lymphomas; germ cell tumours (germinoma, teratoma); sellar region tumours (cranipharyngioma); and metastases. The tumours are classified according to grade. The WHO histological grading scheme used for astrocytomas is based on mitoses, nuclear pleomorphism, necrosis, and endothelial proliferation. WHO Grade I and Grade II tumours are low-grade tumours, and WHO Grade III and Grade IV tumours are high-grade tumours.