**2.3. Group 3 medulloblastomas**

While Wnt and SHH medulloblastomas have been identified by mutations within these pathways, more comprehensive biological pathways have not been delineated for Group 3 and Group 4 medulloblastomas. Hence, these have been so named untilthe underlying biology is further elucidated.

Conventional diagnosis of Group 3 medulloblastomas is accomplished through transcription‐ al profiling [3]. Group 3 medulloblastoma is associated with increased MYC expression and enrichment for photoreceptor pathway-associated genes; these genes are overexpressed in Group 3 [3]. In addition, Group 3 can be divided into subtype based on MYC expression. In Group 3α subtype, all patients contain MYC amplification and this is associated with poor prognosis with increased recurrence and mortality, while the Group 3β subtype contains no MYC amplification and has a prognosis similar to Group 4 medulloblastomas [3]. Medullo‐ blastomas of this group are found in both infants and children, but rarely in adults, and are found more in males than in females [3]. Histologically, Group 3 medulloblastomas frequent‐ ly have large anaplastic cell pathology [3].
