{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,10]],"date-time":"2025-12-10T14:33:54Z","timestamp":1765377234027,"version":"3.46.0"},"reference-count":18,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2025,12,10]],"date-time":"2025-12-10T00:00:00Z","timestamp":1765324800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Background\/Objectives: Ependymomas are central nervous system (CNS) tumors with marked biological and clinical heterogeneity, particularly in pediatric populations. While the 2021 World Health Organization (WHO) classification emphasizes molecular subgroups\u2014posterior fossa type A (PFA) and B (PFB), supratentorial ZFTA fusion-positive (ST-ZFTA), and YAP1 fusion-positive (ST-YAP)\u2014 routine diagnosis is still based on histology and immunohistochemistry (IHC). Recent single-cell RNA sequencing and spatial transcriptomic studies have revealed distinct tumor cell populations, including ependymal-like, astroglial-like, progenitor-like, and stress-associated states. However, a major unresolved issue is whether such heterogeneity can be appreciated and interpreted on conventional pathology slides. Methods: This study examined ependymomas from the Children\u2019s Brain Tumor Network (CBTN), with hematoxylin and eosin (H&amp;E) and IHC for glial fibrillary acidic protein (GFAP) and epithelial membrane antigen (EMA). Tumor regions were stratified into high-cellularity and low-cellularity regions, and staining patterns were correlated with known cellular features from the prior literature. Results: Low-cellularity zones exhibit strong fibrillary GFAP, resembling astroglial or subependymal differentiation. In contrast, high-cellularity zones more often demonstrate variable EMA patterns and GFAP\/EMA-negative compartments, consistent with undifferentiated progenitor-like populations. Perinecrotic areas showed increased GFAP and EMA, possibly reflecting stress-associated cellular states and mesenchymal differentiation. Comparisons between PFA and ST-ZFTA tumors revealed that ST-ZFTA ependymomas were significantly more likely to be hypercellular, with a higher frequency of diffuse EMA expression. In contrast, PFA tumors displayed broader variability with stronger GFAP perinuclear staining. Conclusions: These findings support the concept that conventional histology can capture relevant heterogeneity and may complement molecular studies. The recognition of such features may help refine histopathological assessment and provide practical prognostic insights, particularly in resource-limited settings where molecular testing is not universally available.<\/jats:p>","DOI":"10.3390\/diagnostics15243144","type":"journal-article","created":{"date-parts":[[2025,12,10]],"date-time":"2025-12-10T14:22:40Z","timestamp":1765376560000},"page":"3144","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Histopathological Assessment of Cellular Heterogeneity in Pediatric Ependymomas"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4922-4112","authenticated-orcid":false,"given":"Murad","family":"Alturkustani","sequence":"first","affiliation":[{"name":"Department of Pathology, Faculty of Medicine, King Abdulaziz University, Jeddah 21589, Saudi Arabia"},{"name":"Department of Pathology and Laboratory Medicine, Western University, London, ON N6A 5C1, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,12,10]]},"reference":[{"key":"ref_1","first-page":"161","article-title":"Supratentorial ependymoma","volume":"6","author":"Pajtler","year":"2021","journal-title":"World Health Organization Classification of Tumours: Central Nervous System Tumours"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1097\/NEN.0b013e31816543a6","article-title":"Central nervous system tumors with ependymal features: A broadened spectrum of primarily ependymal differentiation?","volume":"67","author":"Lehman","year":"2008","journal-title":"J. Neuropathol. Exp. Neurol."},{"key":"ref_3","first-page":"159","article-title":"Ependymal tumours: Introduction","volume":"6","author":"Ellison","year":"2021","journal-title":"World Health Organization Classification of Tumours: Central Nervous System Tumours"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"728","DOI":"10.1016\/j.ccell.2015.04.002","article-title":"Molecular Classification of Ependymal Tumors across All CNS Compartments, Histopathological Grades, and Age Groups","volume":"27","author":"Pajtler","year":"2015","journal-title":"Cancer Cell"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"108023","DOI":"10.1016\/j.celrep.2020.108023","article-title":"Single-Cell RNA Sequencing of Childhood Ependymoma Reveals Neoplastic Cell Subpopulations That Impact Molecular Classification and Etiology","volume":"32","author":"Gillen","year":"2020","journal-title":"Cell Rep."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1016\/j.ccell.2020.06.004","article-title":"Single-Cell RNA-Seq Reveals Cellular Hierarchies and Impaired Developmental Trajectories in Pediatric Ependymoma","volume":"38","author":"Gojo","year":"2020","journal-title":"Cancer Cell"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1007\/s00401-023-02682-x","article-title":"Clinically relevant molecular hallmarks of PFA ependymomas display intratumoral heterogeneity and correlate with tumor morphology","volume":"147","author":"Godicke","year":"2024","journal-title":"Acta Neuropathol."},{"key":"ref_8","first-page":"186","article-title":"Subependymoma","volume":"6","author":"Rosenblum","year":"2021","journal-title":"World Health Organization Classification of Tumours: Central Nervous System Tumours"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1007\/s00401-009-0624-y","article-title":"Ependymal cells: Biology and pathology","volume":"119","year":"2010","journal-title":"Acta Neuropathol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1016\/j.ccr.2005.09.001","article-title":"Radial glia cells are candidate stem cells of ependymoma","volume":"8","author":"Taylor","year":"2005","journal-title":"Cancer Cell"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1111\/bpa.12659","article-title":"Childhood supratentorial ependymomas with YAP1-MAMLD1 fusion: An entity with characteristic clinical, radiological, cytogenetic and histopathological features","volume":"29","author":"Andreiuolo","year":"2019","journal-title":"Brain Pathol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3936","DOI":"10.1038\/s41467-022-31683-9","article-title":"Pro-inflammatory cytokines mediate the epithelial-to-mesenchymal-like transition of pediatric posterior fossa ependymoma","volume":"13","author":"Aubin","year":"2022","journal-title":"Nat. Commun."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1615","DOI":"10.3892\/ol.2016.4113","article-title":"Epithelial-mesenchymal transition in glioblastoma progression","volume":"11","author":"Iwadate","year":"2016","journal-title":"Oncol. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"8416","DOI":"10.1038\/s41467-024-51995-2","article-title":"Hypoxia induces ROS-resistant memory upon reoxygenation in vivo promoting metastasis in part via MUC1-C","volume":"15","author":"Godet","year":"2024","journal-title":"Nat. Commun."},{"key":"ref_15","first-page":"3449","article-title":"Ependymal cells undergo astrocyte-like reactivity in response to neuroinflammation","volume":"168","author":"Groh","year":"2024","journal-title":"J. Neurochem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1186\/1477-5751-10-7","article-title":"Histopathological grading of pediatric ependymoma: Reproducibility and clinical relevance in European trial cohorts","volume":"10","author":"Ellison","year":"2011","journal-title":"J. Negat. Results Biomed."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1186\/s40478-021-01215-5","article-title":"Autopsy findings of previously described case of diffuse intrinsic pontine glioma-like tumor with EZHIP expression and molecular features of PFA ependymoma","volume":"9","author":"Alturkustani","year":"2021","journal-title":"Acta Neuropathol. Commun."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1039","DOI":"10.1093\/jnen\/nlae082","article-title":"Utility of OLIG2 immunostaining in pediatric brain tumors with embryonal morphology","volume":"83","author":"Alturkustani","year":"2024","journal-title":"J. Neuropathol. Exp. Neurol."}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/15\/24\/3144\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,12,10]],"date-time":"2025-12-10T14:32:04Z","timestamp":1765377124000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/15\/24\/3144"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,12,10]]},"references-count":18,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2025,12]]}},"alternative-id":["diagnostics15243144"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics15243144","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,12,10]]}}}