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Low-Grade Diffuse Astrocytoma

Last Updated: September 22, 2020

Open Table of Contents: Low-Grade Diffuse Astrocytoma

Figure 1: T1-weighted postcontrast (left) and axial FLAIR (right) images demonstrate a fairly circumscribed infiltrative lesion involving the cortex and white matter. This low-grade tumor is associated with no appreciable enhancement.

Figure 2: Axial FLAIR (top left) and coronal STIR (top right) images demonstrate a poorly defined infiltrative, hyperintense lesion involving the left temporal lobe, left insula, and inferior left frontal lobe. (Bottom) T1WI after contrast administration shows no contrast enhancement of this low-grade astrocytoma.


  • Primary tumor arising from well-differentiated astrocytes


  • WHO grade II
  • Well differentiated, infiltrating, slow growing
  • Malignant degeneration into anaplastic astrocytoma is common


  • Commonly presents with seizures
  • Average patient age, 34 years (20–45 years)
  • Median survival, 6–10 years
    • Survival greater in younger patients, gross-total resection, IDH1-, ARTX-, and MGMT-positive tumors
    • Pontine tumors are associated with decreased survival
  • Sometimes associated with Li-Fraumeni syndrome and Ollier disease


  • General
    • Infiltrating, focal, or diffuse white matter mass that distorts normal architecture
    • Variable size; frontal lobe masses can be large at presentation
    • Tumor commonly extends beyond region of signal abnormality
      • Expansion of involved cortex
    • Two-thirds are supratentorial; frontal lobe involvement is most common
    • One-third are infratentorial; brainstem is most common, cerebellum is uncommonly involved
    • Majority do not enhance
      • Greater degree of enhancement suggests malignant degeneration
    • ±Cysts, calcification (20%)
  • CT
    • Hypodense to isodense, poorly defined, homogenous mass
    • ±Calcification
    • Little to no enhancement on contrast-enhanced CT imaging
  • MRI
    • T1WI: homogenously hypointense
    • T2WI: homogenously hyperintense
    • FLAIR: homogenously hyperintense
    • DWI: no restricted diffusion
    • T1WI+C: little to no enhancement; greater degree of enhancement suggests higher WHO grade
    • MR perfusion: low relative cerebral blood volume (rCBV) relative to anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM); typically, the rCBV ratio to normal white matter is <1.8
    • MRS: mildly elevated choline, mildly depressed N-acetyl aspartate (NAA) peaks and usually no appreciable lactate peak


  • MRI with contrast; consider MR perfusion for equivocal cases

For more information, please see the corresponding chapter in Radiopaedia.

Contributor: Rachel Seltman, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.01.25


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