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:The International Agency for Research on Cancer (Editors: Louis, D.N.; Ohgaki, H.; Wiestler, O.D.; Cavenee, W.K.) (2007). Pathology and Genetics of Tumours of Tumors of the Central Nervous System (IARC WHO Classification of Tumours) (4th ed.). Lyon: World Health Organization. pp. 25. doi:10.1007/s00401-007-0243-4. ISBN 978-9283224303.

• 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!

Histology

• Cell density higher than normal brain.
• Mild to moderate nuclear pleomorphism.
  • Monotony of atypical nuclei hints at neoplasm.
• Cytoplasm highly variable (even within the same tumour).
  • In normal CNS the cytoplasm blends within the neuropil.
• Mitoses absent or very rare.
• Microcystic changes of the background (none to extensive).
• No necrosis, no vascular proliferations.

IHC

• GFAP+ve.
• MAP2+ve (especially in cell processes).
• Vimentin+ve (often perinuclear).
• S-100+ve.
• MIB-1: 0-5% (mean: 2%).
• IDH-1 (R132H)+ve in 60-70%.
• ATRX loss in 70%.

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.

• 

  Astrocytoma, fibrillary type (WC/jensflorian)

• 

  Astrocytoma, protoplasmatic type (WC/jensflorian)

See also

• Astrocytoma.
• Neuropathology_tumours#Infiltrative_astrocytomas