Posterior Fossa Ependymoma, Group B (PFB)

**Semantic type:** Neoplastic Process

**Definition:** A circumscribed ependymoma that arises in the posterior fossa with characteristic DNA methylation patterns including retention of nuclear H3 p.K28me3 (K27me3) expression, absence of CpG island hypermethylation, absence of global DNA hypomethylation, and absence of EZHIP overexpression. Widespread cytogenetic abnormalities are present. Frequent chromosomal aberrations include loss of 22q, monosomy 6, and trisomy 18. It occurs in children older than five years and adults and has a relatively good prognosis.

**Synonyms:** - Group B Posterior Fossa Ependymoma - Group B Posterior Fossa Ependymoma, Adult-Type - Posterior Fossa Ependymoma, Group B (PFB), Adult-Type - Posterior Fossa Group B (PFB) Ependymoma - Posterior Fossa Group B (PFB) Ependymoma), Adult-Type