Medulloblastoma (WNT subgroup)
Medulloblastoma - wingless (WNT) subgroup tumours are the least common medulloblastoma subgroup and have by far the best prognosis. They are usually seen in children and to a lesser degree adults and typically arise from the middle cerebellar peduncle.
WNT tumours account for only 11% of all medulloblastomas, and have, unlike group 3 and 4 tumours, no particular predilection for males, with ~1:1 male to female ratio 1-2.
They are most frequently encountered in children (peak incidence 10-12 years of age), and are also encountered in adults, but almost never in infants 1.
WNT tumours are almost invariably (97%) of classic histology, with the remainder being of large cell/anaplastic morphology 1-2. Interestingly even those with large cell/anaplastic histology have a good prognosis, which is not the case with other subgroups 2.
Most WNT medulloblastomas are sporadic, most frequently the result of mutations of CTNNB1 which encodes for beta-catenin, although numerous other mutations have been described 2. In patients with Turcot syndrome the mutation is of the APC gene 2.
Interestingly, and helpful in preoperative assessment, the WNT subgroup has a distinct predilection for the cerebellar peduncle, bulging into the cerebellopontine angle, which is not usually encountered in other molecular subgroups. They tend to have prominent 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 the WNT subgroup at diagnosis is uncommon, found in only 10% of children, and not seen in adults 1.
WNT tumours have a much better prognosis than all other subtypes of medulloblastoma, in all age groups 1:
- 95% 10-year overall survival of in children
- 100% 5-year overall survival of in adults
- 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
Posterior fossa tumour