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Low-Grade Diffuse Astrocytoma

Last Updated: March 27, 2020

Open Table of Contents: Low-Grade Diffuse Astrocytoma

Figure 1: T1WI post contrast (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 row left) and coronal STIR (top row right) images demonstrate a poorly-defined infiltrative, hyperintense lesion involving the left temporal lobe, left insula and inferior left frontal lobe. T1WI after contrast administration (bottom) shows no contrast enhancement of this low-grade astrocytoma.

Basic Description

  • Primary tumor arising from well-differentiated astrocytes


  • World Health Organization (WHO) grade II
  • Well-differentiated, infiltrating, slow-growing
  • Malignant degeneration into anaplastic astrocytoma common

Clinical Features

  • 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 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 may be large at presentation
    • Tumor commonly extends beyond region of signal abnormality
      • Expansion of involved cortex
    • Two-thirds are supratentorial; frontal lobe involvement most common
    • One-third are infratentorial; brainstem most common, cerebellum uncommonly involved
    • Majority do not enhance

      • Greater degree of enhancement suggests malignant degeneration
    • ± Cysts, calcification (20%)
  • Computed Tomography (CT)

    • Hypo- to isodense, poorly-defined, homogenous mass
    • ± Calcification
    • Little to no enhancement on contrast-enhanced CT
  • Magnetic Resonance Imaging (MRI)

    • T1WI: homogenously hypointense
    • T2WI: homogenously hyperintense
    • Fluid attenuated inversion recovery (FLAIR): homogenously hyperintense
    • Diffusion-weighted imaging (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 less than 1.8
    • MR Spectroscopy: mildly elevated choline, mildly depressed N-acetyl aspartate (NAA) peaks and usually no appreciable lactate peak

Imaging Recommendations

  • 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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