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Pathology High Grade Astrocytoma (HGA)

Anaplastic astrocytoma (WHO grade III) and glioblastoma multiforme (WHO grade IV) are high grade astrocytomas.


Anaplastic astrocytoma:

Macroscopic Features:

  • Generally produces a discernible tumor mass
  • Infiltrates into surrounding brain parenchyma and structures

Microscopic Features:

  • Increased cellularity
  • Nuclear atypia and mitotic activity
  • Cells are enlarged, irregular and have hyperchromatic nuclei
  • Vascular proliferation and necrosis are absent

Genetic Analysis:

High frequency of p53 mutation.  In approximately 50% of cases there is loss of heterozygosity (LOH) on chromosome 19q.  EGFR amplification is rare.


The slide below shows an anaplastic astrocytoma with moderate cellularity, nuclear atypia and a mitotic figure (center).



Glioblastoma Multiforme

Macroscopic Features:

  • Often large mass lesion at the time of diagnosis.
  • Intracranial mass shift.
  • Can extend across myelinated structures such as the corpus callosum resulting in bilateral involvement.
  • Tumor mass generally shows variable coloration, necrosis and hemorrhage.

Microscopic Features:

  • Tumor shows high cellularity, nuclear pleomorphism, necrosis, microvascular proliferation and mitotic activity.
  • Tumor cells are variable in appearance and can be small and undifferentiated, granular, bipolar, fusiform, or large and multinucleated.
  • Infiltrative, and tumor cells accumulate in subpial, subependymal, perivascular and perineuronal regions.
  • Areas of circumscribed necrosis and psudopalisading.

Genetic Analysis:

Glioblastomas in children have different genetic alteration compared with adults; 40% show p53 gene mutations and loss of heterozygosity at 17p.  There is a low frequency of EGFR amplification and a high frequency of LOH on chromosome 10.


The slide below shows a glioblastoma multiforme with high cellularity, necrosis, pseudopalisading and vascular proliferation.





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