Medulloblastoma (group 3)
Medulloblastoma - group 3 tumours are malignant tumours of the central nervous system, and one of the most common pediatric tumours. They typically arise from the vermis of the cerebellum and present in children and infancy. They have the worst prognosis of all medulloblastoma subgroups.
Group 3 tumours account for approximately 27% of all medulloblastomas, and have a predilection for males, with a 2:1 male to female ratio 1.
They are most frequently encountered in children (4-16 years of age) and infants but are rarely seen in adults 1-2.
The majority of Group 3 medulloblastomas have classic or large cell/anaplastic histology 2. They are associated with MYC amplification 2.
The radiographic features of group 3 tumours are similar to group 4 tumours (which we typically associate with medulloblastomas; midline masses arising from the vermis). Unlike group 4 tumours, group 3 tumours tend to be less well defined but have more prominent enhancement 3.
For more details on radiographic features please refer to the general article on medulloblastomas.
Treatment and prognosis
Surgery is the first line of therapy (as is the case in all subgroups) with the aim being histological proof, molecular subtyping and maximal tumour resection, with adjuvant therapy depending on an overall risk profile (see general article on medulloblastoma) 2.
The incidence of CNS metastatic disease in Group 3 tumours at diagnosis is common, found in 30% of all cases, and is even more frequent in infants (47%) 1-2.
Group 3 tumours have the worse prognosis compared to other subtypes of medulloblastoma, similar to group 4 tumours, but significantly worse than SHH and WNT subtypes 1-2:
- 39% 10-year overall survival of in infants
- 50% 10-year overall survival of in children
Prognosis is also influenced by histological subtype.
Posterior fossa tumour
- 1. Kool M, Korshunov A, Remke M et-al. Molecular subgroups of medulloblastoma: an international meta-analysis of transcriptome, genetic aberrations, and clinical data of WNT, SHH, Group 3, and Group 4 medulloblastomas. Acta Neuropathol. 2012;123 (4): 473-84. doi:10.1007/s00401-012-0958-8 - Free text at pubmed - Pubmed citation
- 2. DeSouza RM, Jones BR, Lowis SP et-al. Pediatric medulloblastoma - update on molecular classification driving targeted therapies. Front Oncol. 2014;4: 176. doi:10.3389/fonc.2014.00176 - Free text at pubmed - Pubmed citation
- 3. Perreault S, Ramaswamy V, Achrol AS et-al. MRI surrogates for molecular subgroups of medulloblastoma. AJNR Am J Neuroradiol. 2014;35 (7): 1263-9. doi:10.3174/ajnr.A3990 - Pubmed citation