Glioma

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Gliomas are the most compon primary tumor in the brain and spinal cord. They originate from glial cells and their precursors.

A glioblastoma, the most common glioma. (WC/sbrandner)

Classification

Gliomas are classified by cell type, by CNS WHO grade, patient age and by location.

By type of cell

Gliomas are named according to the specific type of cell with which they share histological features, but not necessarily from which they originate. The main types of gliomas are:

Note: Some authors consider choroid plexus as a specific type of glia, but choroid plexus tumors are usually not covered under the umberella term glioma.

By CNS WHO grade

Gliomas are further categorized according to their grade, which is determined by pathologic evaluation of the tumor. Of numerous grading systems in use, the most common is the World Health Organization (WHO) grading system under which tumors are graded from 1 (least advanced disease—best prognosis) to 4 (most advanced disease—worst prognosis). Historically roman numerals were used for grading, but have been replaced by arabic numerals for grading within tumor types. Specific molecular features may influence tumor grading which is now a combination of histology and molecular neuroathology. Grading is based on expected biological behaviour, although proper treatment may heavily change prognosis.

  • Low-grade gliomas [CNS WHO grade 1-2] are well-differentiated (not anaplastic); these tend to exhibit benign tendencies and portend a better prognosis for the patient. However, they have a uniform rate of recurrence and some diffuse gliomas may increase in grade over time and therefore calling these tumours benign is avoided.
  • High-grade [CNS WHO grade 3-4] gliomas are undifferentiated or anaplastic; these are malignant and carry a worse prognosis.


By patient age group

The fifth CNS WHO edition recognizes following categories:

  • Adult-type diffuse gliomas.
  • Pediatric-type diffuse low-grade gliomas.
  • Pediatric-type diffuse high-grade gliomas.
  • Circumscribed astrocytic gliomas.

By location

  • A supratentorial tumour is above the tentorium, in the cerebrum, and mostly found in adults (70%).
  • An infratentorial tumour is below the tentorium, in the cerebellum, and mostly found in children (70%).
  • The pontine is located in the pons of the brainstem. The brainstem has three parts (pons, midbrain, and medulla); the pons controls critical functions such as breathing, making surgery on these extremely dangerous.
  • Anatomic separation is essential in ependymal tumors. They are classfied into three groups:
    • Supratentorial ependymoma.
    • Posterior fossa ependymoma.
    • Spinal ependymoma.


  • Some gliomas have a specific anatomic designation in their name, reflecting their predominant tumor location.



Table of common gliomas

Histomorphologic comparison of common gliomas:

Entity Rosenthal
fibres / EGBs
Nuclear atypia Mitoses Necrosis MVP Infiltrative Image
Pilocytic astrocytoma yes usu. no usu. no usu. no yes no
Diffuse astrocytoma no yes no no no yes
Anaplastic astrocytoma no yes yes no no yes
Glioblastoma no yes yes yes yes yes
Oligodendroglioma no usu. no yes no no yes
Ependymoma no usu. no usu. no usu. no no discrete
Anaplastic ependymoma no yes yes usu. yes rare discrete

Notes:

  • MVP = microvascular proliferation.
  • EGBs = eosinophilic granular bodies.

Frequency

The relative frequency differs significantly between adults and children.[1]

  • Adults:
    • glioblastoma 55.2%
    • astrocytoma grade II 9%
    • anaplastic astrocytoma grade III 6.1%
    • ependymoma 6.8%
    • oligodendroglioma grade II 5.9%
    • pilocytic astrocytoma 5.9%
    • anaplastic oligodendroglioma grade III 3.3%
    • not further specified 8.4%
  • Children:
    • pilocytic astrocytoma 33.8%
    • malignant glioma, NOS 25.7%
    • ependymoma 11.4%
    • astroyctoma grade II 11.1%
    • glioblastoma 6.3%
    • oligodendroglioma 3.9%
    • anaplastic astrocytoma grade III 3.6%
    • not further specified 4.2%

See also

Neuropathology tumours

Template:References

  1. Ostrom, QT.; Gittleman, H.; Liao, P.; Rouse, C.; Chen, Y.; Dowling, J.; Wolinsky, Y.; Kruchko, C. et al. (Oct 2014). "CBTRUS statistical report: primary brain and central nervous system tumors diagnosed in the United States in 2007-2011.". Neuro Oncol 16 Suppl 4: iv1-63. doi:10.1093/neuonc/nou223. PMID 25304271.