Low-Grade Diffuse Astrocytoma
Last Updated: March 27, 2020
- Primary tumor arising from well-differentiated astrocytes
- World Health Organization (WHO) grade II
- Well-differentiated, infiltrating, slow-growing
- Malignant degeneration into anaplastic astrocytoma 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 associated with decreased survival
- Sometimes associated with Li-Fraumeni syndrome and Ollier disease
- 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
- MRI with contrast; consider MR perfusion for equivocal cases
For more information, please see the corresponding chapter in Radiopaedia.
Contributor: Rachel Seltman, MD
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