Location of the primary tumor was supratentorial in four patients (all supratentorial <i>RELA</i>-fused ependymoma [ST-EPN-RELA]) and within the posterior fossa in five patients (posterior fossa ependymoma type A [PF-EPN-A], <i>n</i> = 4; posterior fossa ependymoma not further classifiable, <i>n</i> = 1), and multifocal in one patient.All four patients with ST-EPN-RELA were alive in first or second complete remission (CR) 7.5-12.3 years after diagnosis.
The molecular groups showed no significant difference in PFS (4-year estimates: posterior fossa ependymoma group A [PF-EPN-A; 42/54], 71.2% ± 8.3%; supratentorial ependymoma positive for v-rel avian reticuloendotheliosis viral oncogene homolog A [ST-EPN-RELA; 8/54], 83.3% ± 17.0%; and supratentorial ependymoma positive for Yes-associated protein [4/54], 100%, P = 0.22).
Recently, recurrent somatic nucleotide variants in histone H3 (H3 K27M) have been reported in group A posterior fossa ependymoma (EPN_PFA), an entity previously described to have no recurrent mutations.
Highly malignant paediatric ependymoma subtypes are Group A tumours of the posterior fossa (PF-EPN-A) and RELA-fusion positive (ST-EPN-RELA) tumours in the supratentorial compartment.