medulloblastoma in peds

Question 1

describe medulloblastoma.

Answer 1

Medulloblastomas are the second most common malignant brain tumor of childhood, with only high-grade gliomas being more common. They most commonly present as midline masses in the roof of the 4th ventricle with associated mass effect and hydrocephalus.

Question 2

Treatment and prognosis of medulloblastoma?

Answer 2

Treatment typically consists of surgical resection, radiation therapy, and chemotherapy, with the prognosis strongly influenced by surgical resection, the presence of CSF metastases at the time of diagnosis, molecular and histological features and expression of the c-erbB-2 (HER2/neu) oncogene.

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Question 3

In the 5th edition (2021) of the WHO classification of CNS tumors, additional subgroups have been recognized based on DNA-methylation profiling and/or transcriptome profiling 17.
What are the groups?

Answer 3

medulloblastoma, WNT-activated

medulloblastoma, SHH-activated

TP53-wildtype

TP53-mutant

subgroups 1-4

non-WNT/non-SHH, further divided into:

group 3 and group 4

subgroups 1-8

Answer 4

WNT (~10%)
children and adults (not seen in infancy)
M:F 1:2

SHH-activated TP53-wildtype (~20%)
infants and adults (rare in children)
M:F 1:1

SHH-activated TP53-mutant (~10%)
children
M:F 3:1

group 3 (~25%)
Infants and children (rare in adults)
M:F 2:1

group 4 (~35%)
Typically children but encountered in all age groups
M:F 3:1

Question 5

Location and outcome in medulloblastoma dependent on group.

Answer 5

cerebellar peduncle/foramen of Luschka

very likely WNT-activated tumors and therefore best prognosis

cerebellar hemisphere

very likely SHH subgroup and therefore intermediate prognosis

likely desmoplastic/nodular/medulloblastoma with extensive nodularity (MBEN)

midline

may be group 3, group 4 or SHH

typically infants with a tumor with ill-defined margins but prominent enhancement: likely group 3 (or SHH) and therefore worst prognosis

typically children with a tumor with well-defined margins but mild or no enhancement: likely group 4 and therefore slightly better prognosis

adults with variably defined and variably enhancing tumors: most likely SHH; hemorrhage raises the probability of group 4 13​