Medulloblastoma - group 4 tumours are malignant tumours of the central nervous system, and one of the most common paediatric tumours. They are the most common medulloblastoma group (followed by group 3, SHH-activated, and WNT-activated), and typically arise from the vermis of the cerebellum.
On this page:
Terminology
The nomenclature and classification of medulloblastomas are rapidly evolving. In the 5th edition (2021) of the WHO classification of CNS tumours, group 3 and group 4 medulloblastomas are grouped together under non-WNT/non-SHH tumours, which is in turn divided into 8 subgroups 5.
Epidemiology
Group 4 tumours account for approximately 34-40% of all medulloblastomas, and have a predilection for males, with a 2:1 male to female ratio 1,4.
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.
Pathology
The majority of grade 4 tumours are of classic histology, with the rest being of large cell / anaplastic histology 2.
Radiographic features
The radiographic features of group 4 tumours are those that 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 groups) 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.
Overall, group 4 tumours have a poor prognosis, somewhat better than group 3 tumours, but significantly worse than SHH and WNT subtypes 1,2. In adults, the prognosis is very poor, whereas in children it is intermediate 4.
Prognosis is also influenced by histological subtype, with large cell/anaplastic histology having a worse prognosis 2.
Unable to process the form. Check for errors and try again.