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
- 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%)
- Hypodense to isodense, poorly defined, homogenous mass
- Little to no enhancement on contrast-enhanced CT imaging
- 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
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