Definition
- Essential:
- A diffuse glioma with mitotic activity occurring in a child or young adult AND
- Absence of mutations in IDH1 or IDH2 AND
- Absence of mutations in H3 genes AND
- Methylation profile aligned with pHGG RTK1, pHGG RTK2, or pHGG MYCN OR
- Key molecular features:
- PDGFRA alteration,
- EGFR alteration, or
- MYCN amplification
- Desirable:
- Microvascular proliferation
- Necrosis, typically palisading
- H3 p.K28me3 (K27me3) retained
Nomenclature
- The terms glioblastoma or paediatric glioblastoma are not recommended.
CNS WHO grading
- Grade 4
Risk factors
- Post therapeutic radiation
- Constitutional mismatch repair deficiency syndrome (CMMRD)
- Lynch syndrome,
- Li-Fraumeni syndrome
Location
- Supratentorial brain
- Brainstem,
- Cerebellum
Molecular Subtypes
- Diffuse paediatric-type high-grade glioma MYCN
- Location
- 86% Supratentorial
- 14% infratentorial
- A more circumscribed lesion,
- Minimal perilesional signal abnormality
- Homogenous contrast enhancement
- Microscopy
- A biphasic pattern with areas of diffuse infiltration and highly cellular circumscribed nodules
- Median OS: 14months
- RTK1 subtype, have not been reported yet
- Location
- 82% Supratentorial
- 18% infratentorial
- Associated with CMMRD and lynch syndrome
- Median OS: 21months
- RTK2 subtype, have not been reported yet.
- Location
- 96% Supratentorial
- 4% infratentorial
- Median OS: 44months
Clinical features
- Seizures
- Depending on location of tumour
Radiology
- Poorly marginated heterogenous lesions most commonly in the cerebral hemisphere.
- Lesions are typically hyperintense on FLAIR with thick,
- Irregular rim enhancement
- Restricted diffusion in the solid components
- pHGG MYCN tumours may be better circumscribed
Prognosis
- Poor
- 2 year survival rate 23.5%
- Median OS: 17.2 months
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