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Posterior fossa A ependymoma (PF-EPN-A)
Source: Childhood Cancer Genomics (PDQ®)–Health Professional Version, National Cancer Institute.
Source updated: April 30, 2025 · Captured 2026-09-09.
Selected source text with whitespace normalised. This Triangle page is not an NCI PDQ summary. Independent clinical review is pending.
The most common posterior fossa ependymoma subgroup is PF-EPN-A and is characterized by the following:
Low rates of variants that affect protein structure, approximately five per genome.[167]
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Gain of chromosome 1q, a known poor prognostic factor for patients with ependymoma,[172] in approximately 25% of cases.[166,168,173]
Loss of chromosome 6q, reported to be a poor prognostic factor for patients with PF-EPN-A, in 8% to 10% of cases.[174]
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A balanced chromosomal profile with few chromosomal gains or losses.[166,167]
Loss of the H3 K27 trimethylation mark and globally hypomethylated DNA.[175] A prospective multi-institutional study analyzed 147 patients with ependymoma. The study reported high sensitivity and specificity for immunohistochemical detection of loss of the H3 K27 trimethylation mark in identifying PF-EPN-A cases.[176] Loss of this mark occurs through multiple mechanisms, including the following:
Loss of the H3 K27 trimethylation mark and globally hypomethylated DNA.[175] A prospective multi-institutional study analyzed 147 patients with ependymoma. The study reported high sensitivity and specificity for immunohistochemical detection of loss of the H3 K27 trimethylation mark in identifying PF-EPN-A cases.[176] Loss of this mark occurs through multiple mechanisms, including the following:
Recurrent variants of EZHIP in 10% of cases, with high EZHIP mRNA expression across almost all PF-EPN-A.[46,177] EZHIP expression (with or without alteration) results in inhibition of the methyltransferase EZH2 leading to loss of the H3 K27 trimethylation mark.[45,46]
Loss of the H3 K27 trimethylation mark and globally hypomethylated DNA.[175] A prospective multi-institutional study analyzed 147 patients with ependymoma. The study reported high sensitivity and specificity for immunohistochemical detection of loss of the H3 K27 trimethylation mark in identifying PF-EPN-A cases.[176] Loss of this mark occurs through multiple mechanisms, including the following:
Recurrent K27M variants in histone H3 variants in a small proportion of cases.[178,179] Unlike diffuse midline gliomas, variants in H3.1 (H3C2 and H3C3) are more common than variants in H3.3 (H3-3A).[177] Histone variants are mutually exclusive with high expression of EZHIP,[177] and they also lead to loss of the H3 K27 trimethylation mark through EZH2 inhibition.
A study that included over 600 cases of PF-EPN-A used methylation array profiling to divide this population into two distinctive subgroups, PFA-1 and PFA-2.[177] Gene expression profiling suggested that these two subtypes may arise in different anatomical locations in the hindbrain. Within both PFA-1 and PFA-2 groups, distinctive minor subtypes could be identified, suggesting the presence of heterogeneity. Additional study will be required to define the clinical significance of these subtypes.
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Publication references
Read the original reference and check its publication notices.
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Preserved source evidence · Independent clinical review pending · Not medical advice