Posterior fossa ependymoma

Intracranial ependymoma in the infratentorial region.

More than 70% of ependymomas occur infratentorially, usually arising from the floor of the fourth ventricle in the midline.

Posterior Fossa Ependymoma Classification.

The PFA molecular subgroup of posterior fossa ependymomas (PF-EPNs) shows poor outcome. H3K27me3 (me3) loss by immunohistochemistry (IHC) is a surrogate marker for PFA wherein its loss is attributed to overexpression of Cxorf67/EZH2 inhibitory protein (EZHIP), C17orf96, and ATRX loss. We aimed to subgroup PF-EPNs using me3 IHC and study correlations of the molecular subgroups with other histone related proteins, 1q gain, Tenascin C and outcome. IHC for me3, acetyl-H3K27, H3K27M, ATRX, EZH2, EZHIP, C17orf96, Tenascin-C, and fluorescence in-situ hybridisation for chromosome 1q25 locus were performed on an ambispective PF-EPN cohort (2003-2019). H3K27M-mutant gliomas were included for comparison. Among 69 patients, PFA (me3 loss) constituted 64%. EZHIP overexpression and 1q gain were exclusive to PFA seen in 72% and 19%, respectively. Tenascin C was more frequently positive in PFA (p = 0.02). H3K27M expression and ATRX loss were noted in one case of PFA-EPN each. All H3K27M-mutant gliomas (n = 8) and PFA-EPN (n = 1) were EZHIP negative. C17orf96 and acetyl-H3K27 expression did not correlate with me3 loss. H3K27me3 is a robust surrogate for PF-EPN molecular subgrouping. EZHIP overexpression was exclusive to PFA EPNs and was characteristically absent in midline gliomas and the rare PFA harbouring H3K27M mutations representing mutually exclusive pathways leading to me3 loss 1).

Chen et al. found that nucleolin was an unfavorable prognostic predictor for ependymomas. Moreover, the findings show a subset of aggravating outcomes in anaplastic ependymoma and infratentorial ependymoma. 2).

All surgical procedures for posterior fossa ependymomas performed since 2001 in the Department of Neurosurgery, University Medicine Greifswald, were analysed.

8 patients (2f, 6m, mean age 41.9 years, range from 29 to 56 years) underwent surgery for posterior fossa ependymoma. All tumors were WHO°II. Tumor adherence was found to be in the caudal rhomboid fossa (between the obex and striae medullare, but below the facial colliculus) in all patients. The four-hand suction-irrigation technique led to gross total resection in all patients (100%) without significant permanent neurological deficits after surgery. None of the patients got further treatment (chemotherapy, radiation therapy, second surgery). In none of these patients, tumor recurrence was seen on MRI after a mean follow-up of 102 months (ranging from 14 to 181 months).

Long-term progression free survival in adult patients suffering from posterior fossa ependymoma is possible by gross total resection without adjuvant radio- or chemotherapy. By careful bimanual microsurgical dissection using the four-hand suction-irrigation technique and avoidance of bipolar coagulation on the floor of the fourth ventricle, the risk for permanent neurological deficits is low 3).

A 13-year-old boy with severe clinical symptoms and signs underwent surgery for a posterior fossa ependymoma in 1954. The tumor was adjacent to the floor of the fourth ventricle, and surgery was complicated by profound bleeding. Therefore, only a partial resection was performed. Postoperative radiotherapy was given to the posterior fossa. The recovery was uneventful, and he has been in full-time work until the age of 62 years and is now 74 years old. Repeated MRI scans demonstrate a stable residual fourth ventricular tumor 4)

Nambirajan A, Sharma A, Rajeshwari M, Boorgula MT, Doddamani R, Garg A, Suri V, Sarkar C, Sharma MC. EZH2 inhibitory protein (EZHIP/Cxorf67) expression correlates strongly with H3K27me3 loss in posterior fossa ependymomas and is mutually exclusive with H3K27M mutations. Brain Tumor Pathol. 2020 Nov 1. doi: 10.1007/s10014-020-00385-9. Epub ahead of print. Erratum in: Brain Tumor Pathol. 2021 Jan 9;: PMID: 33130928.
Chen C, Chen L, Yao Y, Qin Z, Chen H. Nucleolin overexpression is associated with an unfavorable outcome for ependymoma: a multifactorial analysis of 176 patients. J Neurooncol. 2015 Nov 28. [Epub ahead of print] PubMed PMID: 26615563.
Marx S, El Refaee E, Langner S, Schroeder HWS. Four-hand suction-irrigation technique leads to gross total resection and long-term-progression free survival in fourth ventricular ependymoma. World Neurosurg. 2017 Aug 10. pii: S1878-8750(17)31305-0. doi: 10.1016/j.wneu.2017.08.008. [Epub ahead of print] PubMed PMID: 28804042.
Lundar T, Due-Tønnessen BJ, Krossnes B, Due-Tønnessen P, Brandal P. Posterior fossa ependymoma in childhood: 60 years event-free survival after partial resection—a case report. Childs Nerv Syst. 2015 Sep;31(9):1573-6. doi: 10.1007/s00381-015-2766-7. Epub 2015 Jun 6. PubMed PMID: 26047947; PubMed Central PMCID: PMC4560763.
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