Astrocytic tumours

Astrocytic tumours are primary central nervous system tumours that either arises from astrocytes or appear similar to astrocytes on histology having arisen from precursor cells. They are the most common tumours arising from glial cells and can be broadly divided into three groups: 

1. diffuse, adult-type

2. diffuse, paediatric type

3. circumscribed

These can further be divided into individual entities as described in the WHO classification of CNS tumours (5^th edition, 2021), many of which are molecularly defined ³. 

• adult-type diffuse gliomas 

  • astrocytoma, IDH-mutant: WHO CNS grade 2 to 4

  • glioblastoma, IDH-wildtype: WHO CNS grade 4 

• paediatric-type diffuse low-grade gliomas

  • angiocentric glioma: WHO CNS grade 1

  • diffuse astrocytoma, MYB- or MYBL1-altered: WHO CNS grade 1

  • diffuse low-grade glioma, MAPK pathway-altered: grade not assigned

• paediatric-type diffuse high-grade gliomas

  • diffuse midline glioma, H3 K27-altered: WHO CNS grade 4

  • diffuse hemispheric glioma, H3 G34-mutant: WHO CNS grade 4

  • diffuse paediatric-type high-grade glioma, H3-wildtype and IDH-wildtype: WHO CNS grade 4

  • infant-type hemispheric glioma: grade not assigned

• circumscribed astrocytic gliomas

  • pilocytic astrocytoma: WHO CNS grade 1

    • pilomyxoid astrocytoma: WHO CNS grade 2

  • high-grade astrocytoma with piloid features: grade not assigned

  • pleomorphic xanthoastrocytoma: WHO CNS grade 2 or 3

  • subependymal giant cell astrocytoma: WHO CNS grade 1

  • chordoid glioma: WHO CNS grade 2

  • astroblastoma, MN1-altered: grade not assigned

Additionally, some tumours also contain astrocytic components, and it is often this component that dictates biological behaviour. Examples include:

• ganglioglioma

Most of these tumours have strikingly differing demographics, imaging appearances, treatment and prognosis and thus they are, along with spinal astrocytomas discussed separately.

Note: anaplastic astrocytoma, gliomatosis cerebri, fibrillary astrocytoma and protoplasmic astrocytoma, gemistocytic astrocytoma are no longer recognised as distinct entities in the WHO classification of CNS tumours.