Medulloblastoma (group 4)
Medulloblastoma - group 4 tumours are malignant tumours of the central nervous system, and one of the most common pediatric tumours. They are the most common medulloblastoma subgroup (followed by group 3, SHH and WNT), and typically arise from the vermis of the cerebellum.
Group 4 tumours account for approximately 34% 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), not infrequently in adults (second only to SHH in frequency) and are uncommon in infants 1.
The majority of grade 4 tumours are of classic histology, with the rest being of large cell / anaplastic histology 2.
The radiographic features of group 4 tumours are those which we typically associate with medulloblastomas; midline masses arising from the vermis. They are fairly well defined with limited contrast 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 4 tumours at diagnosis is common, found in 31% of all cases, and is even more frequent in infants (36%) 1.
Group 4 tumours have a poor prognosis, somewhat better than group 3 tumours, but significantly worse than SHH and WNT subtypes 1-2.
Prognosis is also influenced by histological subtype, with large cell / anaplastic histology having a worse prognosis 2.
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