There are two principal histological subtypes, namely classic (∼70%) and anaplastic ependymoma (∼30%).
Subependymoma 9383/1 WHO grade I
Myxopapillary ependymoma 9394/1 WHO grade I
–Papillary ependymoma 9393/3 (WHO grade II)
–Clear cell ependymoma 9391/3 (WHO grade II)
–Tanycytic ependymoma 9391/3
Anaplastic ependymoma 9392/3 (WHO grade III).
Increasingly, as is the case with many other tumors, molecular classification is proving to be more important than histological classification in predicting treatment response and prognosis. Intracranial ependymomas can be divided into four main groups that correlate largely with location:
Posterior fossa type A ependymoma: H3 K27 trimethylation
Posterior Fossa B
RELA fusion (discussed separately)
Of nine ependymoma molecular groups detected by DNA methylation profiling, the posterior fossa type A (PFA) is most prevalent.