Medulloblastoma (group 4)

Medulloblastoma - group 4 tumors are malignant tumors of the central nervous system, and one of the most common pediatric tumors. They are the most common medulloblastoma subgroup (followed by group 3, SHH, and WNT), and typically arise from the vermis of the cerebellum.

Epidemiology

Group 4 tumors account for approximately 34-40% of all medulloblastomas, and have a predilection for males, with a 2:1 male to female ratio .

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 .

Pathology

The majority of grade 4 tumors are of classic histology, with the rest being of large cell / anaplastic histology .

Radiographic features

The radiographic features of group 4 tumors are those which we typically associate with medulloblastomas; midline masses arising from the vermis. They are fairly well defined with limited contrast enhancement .

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 tumor resection, with adjuvant therapy depending on an overall risk profile (see general article on medulloblastoma) .

The incidence of CNS metastatic disease in Group 4 tumors at diagnosis is common, found in 31% of all cases, and is even more frequent in infants (36%) .

Overall, group 4 tumors have a poor prognosis, somewhat better than group 3 tumors, but significantly worse than SHH and WNT subtypes . In adults the prognosis very poor, whereas in children it is intermediate .

Prognosis is also influenced by histological subtype, with large cell/anaplastic histology having a worse prognosis .