Summary and Further Reading

Chapter 3 - Histology and Molecular Pathology of Gliomas


  • Gliomas form a very heterogeneous group of tumours, with regard to both histology and clinical behaviour
  • Based on histology, gliomas are traditionally typed as astrocytic, oligodendroglial and ependymal neoplasms, and graded as low grade (WHO Grade 2), anaplastic (WHO Grade 3), or (only for astrocytic tumours) glioblastoma (WHO Grade 4)
  • The vast majority of astrocytomas and oligodendrogliomas in adult patients are so-called diffuse gliomas, characterised by diffuse infiltrative growth in the CNS parenchyma
  • Three major molecular categories of diffuse gliomas are recognised: IDH wildtype; IDH mutant & 1p/19q non-codeleted; IDH mutant & 1p/19q codeleted
  • IDH wildtype and IDH mutant & 1p/19q non-codeleted diffuse gliomas generally show an astrocytic Phenotype, most IDH mutant & 1p/19q codeleted gliomas exhibit oligodendroglial features
  • According to the WHO 2016 classification, demonstration of 1p/19q codeletion is required for the diagnosis of “canonical” oligodendroglioma
  • Most glioblastomas (about 90%) are IDH wildtype; IDH mutant glioblastomas often originate from lower grade (Grade 2 or 3) diffuse astrocytomas
  • The majority of the lower grade diffuse astrocytomas and all oligodendrogliomas are IDH1 or IDH2 mutant (IDH1 R132H being by far the most frequent mutation)
  • Diffuse gliomas in children are generally IDH wildtype and have a different molecular pathogenesis compared to histologically similar tumours in adults
  • Non-diffuse gliomas are more frequent in children. The most common representatives of this group are the relatively benign pilocytic astrocytomas and the variably aggressive ependymomas

Further Reading

Aldape K, Zadeh G, Mansouri S, et al. Glioblastoma: pathology, molecular mechanisms and markers. Acta Neuropathol 2015; 129:829–848.

Claes A, Idema AJ, Wesseling P. Diffuse glioma growth: a guerilla war. Acta Neuropathol 2007; 114:443–458.

Collins VP, Jones DT, Giannini C. Pilocytic astrocytoma: pathology, molecular mechanisms and markers. Acta Neuropathol 2015; 129:775–788.

Ichimura K, Narita Y, Hawkins CE. Diffusely infiltrating astrocytomas: pathology, molecular mechanisms and markers. Acta Neuropathol 2015; 129:789–808.

Louis DN, Ohgaki H, Wiestler OD, et al (Eds). WHO Classification of Tumours of the Central Nervous System, 4th edition, revised. Lyon: IARC Press, 2016.

Olar A, Wani KM, Alfaro-Munoz KD, et al. IDH mutation status and role of WHO grade and mitotic index in overall survival in grade II-III diffuse gliomas. Acta Neuropathol 2015; 129:585–596.

Ostrom QT, Gittleman H, Liao P, et al. CBTRUS statistical report: primary brain and central nervous system tumors diagnosed in the United States in 2007-2011. Neuro Oncol 2014; 16(Suppl 4): iv1–iv63.

Pajtler KW, Witt H, Sill M, et al. Molecular classification of ependymal tumors across all CNS compartments, histopathological grades, and age groups. Cancer Cell 2015; 27:728–743.

Reuss DE, Kratz A, Sahm F, et al. Adult IDH wild type astrocytomas biologically and clinically resolve into other tumor entities. Acta Neuropathol 2015; 130:407–417.

Wesseling P, van den Bent M, Perry A. Oligodendroglioma: pathology, molecular mechanisms and markers. Acta Neuropathol 2015; 129:809–827.

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Last update: 18 September 2017