Diffuse astrocytoma

Diffuse astrocytoma (AKA: diffuse, low-grade astrocytoma) is a infiltrating astrocytoma occurring in the CNS white matter.

• Most common grade II WHO glioma in adults (peaks between 30-40 years).
• 10-15% of all astrocytomas.
• Usually shows progression to glioblastoma sooner or later.

Previously categorized as follows:

• Diffuse astrocytoma ICD-O: 9400/3
  • Fibrillary astrocytoma ICD-O: 9420/3 - most frequent
  • Gemistocytic astrocytoma ICD-O:9411/3
  • Protoplasmatic astrocytoma ICD-O:9410/3 - rare

Note: This subtyping is no longer in use!

Radiology/Clinic

• Mass effect.
• Seizures.
• Neurologic decifit.
• Usually not contrast-enhanching, T2 bright.

Macroscopy

• No clear demarcation from white matter
• May contain larger cysts
• No necrosis

Histology

Features:

• Cell density higher than normal brain.
• Mild to moderate nuclear pleomorphism.
  • Monotony of atypical nuclei and irregular distribution indicates neoplasm.
  • "naked nuclei" without recognizeable processes.
  • No prominent nucleolus.
• Cytoplasm highly variable (even within the same tumour).
  • In normal CNS the cytoplasm blends within the neuropil.
• Mitoses absent or very rare.
• Microcystic spaces of the background (none to extensive).
• No necrosis, no vascular proliferations.
  • Except radiation necrosis.
• Lymphocytic cuffing (mostly in gemistocytic type)
• Abent to few rosenthal fibers.

• 

  Diffuse astrocytoma, H&E (WC/jensflorian)

• 

  Diffuse astrocytoma, H&E (WC/jensflorian)

• 

  Astrocytoma, fibrillary type (WC/jensflorian)

• 

  Astrocytoma, protoplasmatic type (WC/jensflorian)

IHC

• GFAP+ve.
• MAP2+ve (especially in cell processes).
• Vimentin+ve (often perinuclear).
• S-100+ve.
• p53: Nuclear staining in 30% of the tumours (usually few cells).
• MIB-1: 0-5% (mean: 2%).
• IDH-1 (R132H)+ve in 60-70%.
• ATRX loss in 70%.

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  GFAP in astrocytoma (WC/jensflorian)

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  ATRX loss in astrocytoma (WC/jensflorian)

Molecular

• Absence of LOH 1p/19q.
• Tp53 mutations in approx. 60% (80-90% in gemistocytic, 50% in fibrillary types).
• MGMT promotor methylated in approx. 50%.

DDx

• Reactive astrocytosis.
• Demyelinisation.
• Anaplastic astrocytoma
• Oligoastrocytoma
• Oligodendroglioma - esp. protoplasmatic forms.
• SEGA - esp. gemistocytic forms.

See also

• Astrocytoma.
• Neuropathology_tumours#Infiltrative_astrocytomas