Definition
- Diffuse astrocytoma without histological features of anaplasia AND
- With genetic alterations in MYB or MYBL1 AND
- Structural variant of MYB or MYBL1
- DNA methylation profile aligned with diffuse astrocytoma, MYB- or MYBL1altered
- Absent
- Mutations in IDH or H3 genes
Genetic
- MYB proto-oncogene
- Regulates cyclin-dependent kinases (Cdks) expression and activity, essential for cell duplication
Numbers
- Rare (2% of all paediatric low-grade gliomas)
- Infiltrative neoplasm designated a CNS WHO grade 1 [65].
- The largest series to date reported on twenty patients with a median age of 29 years [66].
- Paediatric studies so far included less than 11 patients [67–69].
Location
- Supratentorial
- Temporal lobe (42.5% of cases)
- Frontal lobe
- Occipital lobe
- With cortical and subcortical involvement Children with this tumour typically present with drug-resistant epilepsy with the median age of onset of 10 years
Histopathology
- Microscopic
- A diffusely infiltrative astroglial neoplasm composed of monomorphic cells
Imaging
- Imaging descriptions are of hyperintensity or mixed signal intensity on FLAIR without (or minimal) enhancement or diffusion restriction
- Focal and diffuse growth patterns have been observed, and large cysts have been reported
- T2w (A) shows
- A diffusely infiltrating tumour of the left parietal and temporal white matter.
- There is mass effect on basal ganglia, thalamus, and corpus callosum with midline shift.
- There is peripheral high FLAIR signal (B) without enhancement on T1w-CE (C) or restricted diffusion on ADC (D)
- Methylation profiling:
- Low grade glioma,
- MYB/MYBL1.
Prognosis
- Limited data
- Relatively benign course with 9 of 11 children stable or even showing disease resolution over a 12-year follow-up
- For those presenting with drug-resistant epilepsy, surgery appears effective with 90% becoming seizure-free following resection
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