Definition
- Essential:
- A medulloblastoma AND
- Wildtype TP53 gene AND
- SHH pathway activation OR
- A DNA methylation profile aligned with SHH-activated medulloblastoma
Numbers
- Bimodal: aged < 4 years and adolescents
CNS WHO grading
- Grade 4
Localisation
- Same as TP53 mutant
Origin
- Same as TP53 mutant
Immunophenotype
- Same for all medulloblastoma
Pathology
- Firm (reflecting intratumoural desmoplasia) and circumscribed.
- Histological subtype
- Classic
- Standard-risk tumour
- Large cell / anaplastic
- Tumour of uncertain clinicopathological significance
- Desmoplastic / nodular
- Low-risk tumour in infants; prevalent in infants and adults
- Extensive nodularity
- Low-risk tumour of infancy
Genetic profile
- Can be associated with
- Germline or somatic mutations in the negative regulators PTCH1 or SUFU,
- Activating somatic mutations in SMO or (rarely) amplification of GLI2.
Prognosis
- 5-year overall survival 76% for those with a TP53-wildtype tumour.
- TP53 mutation will only affect prognosis in the SHH activated group of medulloblastoma but not affect prognosis in WNT activated medulloblastomas
- Classic or large cell / anaplastic morphology have a worse outcome than the two types of desmoplastic medulloblastoma
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