[WHO classification of tumours of the CNS: revised edition of 2007 with critical comments on the typing und grading of common-type diffuse gliomas].

The fourth edition of the WHO classification of tumours of the CNS was published in 2007. Six new entities were codified: angiocentric glioma (AG); papillary glioneuronal tumour (PGNT); rosette-forming glioneuronal tumour of the fourth ventricle (RGNT); papillary tumour of the pineal region (PTPR); spindle cell oncocytoma of the adenohypophysis (SCO); and pituicytoma. Furthermore, six histological variants of well-known brain tumours have been added, partially because they show different biological behaviour and/or prognosis: pilomyxoid astrocytoma; atypical choroid plexus papilloma; medulloblastoma with extensive nodularity; anaplastic medulloblastoma; extraventricular neurocytoma; non-specific variant of dysembryoplastic neuroepithelial tumour (DNT). The new entities and variants are discussed in this review. Moreover, the typing und grading of common-type diffuse gliomas, as well as the WHO grading system, are critically reviewed, particularly with regard to the prognostically important differential diagnosis of diffuse astrocytomas und oligodendrogliomas.