Posterior Fossa Ependymoma with Chondro-Osseous Metaplasia in a Child: A Rare Case Report

Posterior Fossa Ependymoma with Chondro-Osseous Metaplasia in a Child: A Rare Case Report | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report Posterior Fossa Ependymoma with Chondro-Osseous Metaplasia in a Child: A Rare Case Report Batoul Amraya, Matthew Nseir, Kawthar Alawad, Abdulkader Amraya, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9165736/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Background Ependymomas are glial tumors characterized by perivascular pseudorosettes. The presence of chondro-osseous metaplasia in these tumors is extremely rare with fewer than 10 cases reported in the literature. Case presentation We report a 4-year-old girl who presented with headaches, progressive gait disturbance and dizziness. Neurological examination revealed cerebellar signs and bilateral papilledema. MRI showed a posterior fossa mass with obstructive hydrocephalus. Histopathological examination confirmed a WHO Grade II ependymoma with areas of chondro-osseous metaplasia. At 4-months follow-up, there was no recurrence. Conclusion The etiology and prognosis of these histopathological variants remain unclear due to the limited number of reported cases. This case highlights the clinical presentation, pathological characteristics, and outcome of an ependymoma with chondro-osseous metaplasia. Ependymoma Chondro-osseous metaplasia Posterior fossa tumor Pediatric brain tumor Histopathological variant Central nervous system neoplasm Case report Figures Figure 1 Figure 2 Figure 3 Background Ependymomas are rare neuroepithelial tumors of the central nervous system, representing only 1.6–1.8% of primary CNS neoplasms. They arise through oncogenetic alterations in tumor cells that promote ependymal differentiation. Typically, these tumors are well-circumscribed and originate from ependymal cells lining the ventricular system and the central canal of the spinal cord.[ 1 ] Approximately half of all ependymomas occur in children, most often in the posterior fossa, making them the second most common solid brain tumor in the pediatric population after medulloblastoma. In children aged 1–14 years, ependymomas account for about 5.7% of all diagnosed CNS tumors, with an estimated annual incidence of 0.30 per 100,000 individuals. The incidence is reported to be higher in males.[ 2 ] Ependymomas demonstrate a bimodal age distribution. The first peak occurs in childhood, with a mean age of presentation around 4 years, and these tumors most often arise intracranially, predominantly in the posterior fossa, followed by supratentorial sites. A second peak is seen in adults, typically between 20 and 40 years of age, where ependymomas usually present as intramedullary spinal tumors [ 1 ] According to earlier WHO grading schemes, ependymomas were divided into three categories: myxopapillary (Grade I), conventional (Grade II), and anaplastic (Grade III). However, the 2021 WHO Classification of CNS Tumors (CNS5) has revised this approach, emphasizing molecularly defined subgroups and reclassifying myxopapillary ependymoma as Grade II. Current diagnostic practice integrates both histological features and molecular markers, with supratentorial, posterior fossa, and spinal ependymomas now further stratified by genetic alterations such as ZFTA and YAP1 fusions, or MYCN amplification.[ 3 ][ 4 ] A survey of the English language literature has identified approximately 15 documented cases of ependymomas exhibiting chondroosseous metaplasia. These rare histopathological patterns account for only about 0.5% of all diagnosed ependymomas. The occurrence of cartilaginous or osseous differentiation within gliomas is exceedingly uncommon and has been most often recognized in fourth ventricular ependymomas and midline astrocytomas.[ 2 ] Case Presentation A 4-year-old female was admitted with a history of severe headache, often awakening her from sleep. The headache was persistent and unresponsive to analgesics. Over time, she developed progressive gait disturbance, imbalance, and dizziness. On neurological examination, fingertonose testing revealed dysmetria, consistent with cerebellar dysfunction. Her gait was broad-based, and she exhibited medial strabismus (esotropia). The Babinski sign was negative, suggesting no upper motor neuron involvement. There were no clinical signs of meningeal irritation or increased intracranial pressure. However, fundoscopy revealed bilateral papilledema, confirming raised intracranial pressure at the optic discs. Radiological evaluation with CT and MRI demonstrated a posterior fossa mass extending to the right side, compressing the brainstem and associated with ventricular dilatation consistent with obstructive hydrocephalus (Fig. 1 ). Histopathological Findings: An excisional biopsy was performed on the posterior fossa mass. The specimen was received in two containers, the first measuring 4.5 × 3 × 0.7 cm and the second measuring 6.5 × 5 × 1.3 cm. Microscopic examination demonstrated monomorphic cells with clear cytoplasm, fine nuclear chromatin, and inconspicuous nucleoli. The tumor cells exhibited fibrillary cytoplasmic processes that condensed in a collar like fashion around stromal blood vessels, forming perivascular pseudorosettes and occasional true rosettes (Fig. 2 ). Areas of dystrophic calcification were identified, along with foci of chondro-osseous metaplasia (Fig. 3 ). Importantly, no tumor necrosis was observed. Based on these findings, the lesion was concluded to represent an ependymoma (WHO Grade II), excised from the posterior fossa. Ancillary studies are pending, with EMA and Ki67 immunostains currently in processing. Postoperative Course: Following excisional biopsy, the patient developed clear esotropia and peripheral facial nerve palsy. Pupils remained equal and reactive. Cardiovascular and respiratory examinations were normal, with a full bounding pulse and unremarkable auscultation. The abdomen was soft, with palpable hepatomegaly. No seizures or vomiting were observed. A vesicular clustered rash on an erythematous base was noted over the right thigh and upper left gluteal region, consistent with herpes simplex infection. The patient was subsequently administered appropriate medications tailored to these findings. After treatment, she demonstrated improvement in her general condition and neurological status. Discussion Ependymomas are neuroepithelial tumors that develop from ependymal cells lining the cerebral ventricles. Their incidence ranges from 0.29 to 0.6 per 100,000 according to the Central Brain Tumor Registry of the USA. These tumors comprise between 1.6 and 1.8 of all primary CNS tumors, with higher incidence among children, and show slightly male predominance [ 1 ]. Cartilaginous metaplasia with or without bone formation is an exceptionally rare finding in ependymomas.[ 7 ] Because of its rarity, its development and impact on prognosis are not clear yet. Few theories have tried to explain the mechanism behind the chondro-osseous metaplasia. The most accepted theory suggests that these changes arise from metaplastic transformation of neoplastic glial or mesenchymal tissue. [ 6 ] Another theory proposes that glial tumor cells may produce a material that is similar to the basement membrane which can condense and transform into mesenchymal tissue.[ 1 ] Güzey et al. suggested that the cartilage found in ependymoma case, might have developed from a transformation of the neuroepithelial cells to mesenchymal cells, as the cartilaginous tissue showed no fibrous capsule and immunoreacted positively to glial fibrillary acidic protein (GFAP) antibody [ 2 ]. Despite the proposed theories, the exact etiopathogenesis of these metaplastic change sin ependymomas remains unclear, because of the rarity of this histopathological finding. Wang et al. reported that ependymomas with cartilaginous metaplasia may be associated with a worse prognosis despite aggressive therapy. [ 7 ] In contrast, Gessi et al. performed a case series of 13 rare histological ependymoma variants including four patients with cartilaginous-osseous ependymoma, and they could not identify an association between the tumor grade and the presence of chondro-osseous metaplasia.[ 8 ] These conflicting findings could be due to the small number of reported cases, histological diversity and tumor grade, location and extent of tumor resection. As a result, the effect of this metaplasia on tumor prognosis is poorly understood. According to the 2021 WHO classifications of CNS tumors, diagnosis of ependymomas now depends on a combination of histopathological and molecular findings as well as anatomic tumor location. [ 4 ] This updated classification includes supratentorial ependymomas that are positive for ZEFTA fusion; supratentorial ependymomas positive for YAP1 fusion; posterior fossa ependymomas of group A and group B; as well as spinal ependymomas with MYCN amplification. [ 9 ] In the present case the tumor was classified as WHO Grade II based on histopathological features, however, molecular testing could not be performed. Management of Ependymomas includes gross total resection with or without adjuvant radiotherapy.[ 1 ] Previously reported cases in the literature are summarized in Table 1 , including the case reported by Bannykh et al. [ 11 ]. Most reported cases are among children and show a predilection for the posterior fossa. Several cases with high grade tumor are associated with poor prognosis. In contrast, the present case shows favorable short-term outcome with no recurrence at 3 months follow-up. Table 1 Previously reported cases of ependymoma with cartilaginous-osseous metaplasia Number First author Age (years) Gender Location Histology WHO grade Follow-up and outcome 1 Wang X⁷ 5 Male Fourth ventricle Ependymoma 2 Death at 18 months 2 Mridha AR¹⁰ 9 Male Left cerebellopontine angle cistern Anaplastic 3 Not available 3 Gessi M⁸ 2 Female Fourth ventricle Anaplastic 3 Not available 3 Female Fourth ventricle Ependymoma 2 Not available 53 Female Fourth ventricle Subependymoma/ Ependymoma 1 Not available 4 Bannykh S¹¹ 61 Male Left frontal lobe Anaplastic 3 Death at 6 months 5 Alkhaibary A² 3 Male Fourth ventricle Anaplastic 3 No recurrence at 2 years 6 Shaivy M¹ 7 Male Right cerebellopontine angle cistern Posterior fossa ependymoma 3 Death at 9 months post-surgical excision 7 Present case 4 Female Fourth ventricle Ependymoma 2 No recurrence at 4 months This table summarizes all published cases of ependymomas presenting with chondro‑osseous metaplasia, including patient age, gender, tumor location, histological type, WHO grade, and follow-up outcomes. Abbreviations: F, female; M, male; WHO, World Health Organization; NR, not reported. All tumors were confirmed by histopathology, and follow-up periods are indicated where available. Superscript numbers correspond to references in the manuscript. Conclusion This case describes a posterior fossa ependymoma with chondro-osseous metaplasia. Reporting more cases with long-term follow-up and thorough examination is crucial to improve understanding of its pathogenesis and prognostic significance. Abbreviations CNS – Central nervous system CT – Computed tomography EMA – Epithelial membrane antigen GFAP – Glial fibrillary acidic protein MRI – Magnetic resonance imaging WHO – World Health Organization CNS5 – 2021 World Health Organization Classification of Tumors of the Central Nervous System Declarations Ethics approval and consent to participate The study was conducted in accordance with the Declaration of Helsinki. Ethical approval was obtained from the Ethics Committee of Aleppo University Hospital, Syria. Written informed consent was obtained from the patient’s legal guardian for participation in this case report. Consent for publication Written informed consent was obtained from the patient’s legal guardian for publication of this case report and accompanying images. A copy of the consent form is available for review by the Editor-in-Chief. Competing interests The authors declare that they have no competing interests. Clinical trial number Not applicable Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Author Contribution SA supervised and helped in writing the manuscript.BA, MN, KA and AA wrote the manuscript. KA performed histopathological examination. All authors read and approved the final manuscript. Acknowledgement We would like to acknowledge the use of ChatGPT, for its assistance in enhancing the language. Data Availability The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. References Malik S, Samanta SS, Kolte S. Posterior fossa ependymoma in a child with extensive chondro-osseous metaplasia occurring at cerebellopontine angle and masquerading as a vestibular schwannoma: an exceptionally rare clinicopathological manifestation with review of literature. J Neurol Surg Rep. 2024;85(3):e132–7. https://doi.org/10.1055/a-2372-6701 . Alkhaibary A, AlSufiani F, Alassiri AH, Almuntashri M, Al Qutub ST. Chondro-osseous metaplasia in ependymoma: a rare histopathological finding. Case Rep Pathol. 2020;2020:1528698. 10.1155/2020/1528698 . Louis DN, Perry A, Reifenberger G, von Deimling A, Figarella-Branger D, Cavenee WK, et al. The 2016 World Health Organization classification of tumors of the central nervous system: a summary. Acta Neuropathol. 2016;131(6):803–20. https://doi.org/10.1007/s00401-016-1545-1 . Louis DN, Perry A, Wesseling P, Brat DJ, Cree IA, Figarella-Branger D, et al. The 2021 WHO classification of tumors of the central nervous system: a summary. Neuro Oncol. 2021;23(8):1231–51. https://doi.org/10.1093/neuonc/noab106 . Ormond DR, Hadley C, Gressot LV. Current management of adult ependymoma. Curr Treat Options Oncol. 2022;23(9):1185–99. https://doi.org/10.1007/s11912-022-01260-w . Chakraborti S, Govindan A, Alapatt JP, Radhakrishnan M, Santosh V. Primary myxopapillary ependymoma of the fourth ventricle with cartilaginous metaplasia: a case report and review of the literature. Brain Tumor Pathol. 2012;29(1):47–52. https://doi.org/10.1007/s10014-011-0064-y . Wang X, Zhang S, Ye Y, Chen Y, Liu X. Ependymoma with cartilaginous metaplasia might have more aggressive behavior: a case report and literature review. Brain Tumor Pathol. 2012;29(3):172–6. https://doi.org/10.1007/s10014-011-0079-4 . Gessi M, Kuchelmeister K, Lauriola L, Pietsch T. Rare histological variants in ependymomas: histopathological analysis of 13 cases. Virchows Arch. 2011;459(4):423–9. 10.1007/s00428-011-1126-6 . Ellison DW, Aldape KD, Capper D, Fouladi M, Gilbert MR, Gilbertson RJ, Hawkins C, Merchant TE, Pajtler K, Venneti S, Louis DN. cIMPACT-NOW update 7: advancing the molecular classification of ependymoma. Acta Neuropathol. 2021;142(5):809–12. 10.1007/s00401-021-02367-z . Mridha AR, Sharma MC, Sarkar C, Garg A, Singh MM, Suri V. Anaplastic ependymoma with cartilaginous and osseous metaplasia: report of a rare case and review of literature. J Neurooncol. 2007;82(1):75–80. 10.1007/s11060-006-9239-5 . Bannykh S, Baehring JM. Images in neuro-oncology: rapid development of osseous and chondrous metaplasia in recurrent anaplastic ependymoma. J Neurooncol. 2007;81(3):257–8. 10.1007/s11060-006-9225-y . Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 15 May, 2026 Reviews received at journal 11 May, 2026 Reviewers agreed at journal 05 May, 2026 Reviewers agreed at journal 04 May, 2026 Reviewers agreed at journal 26 Apr, 2026 Reviewers invited by journal 24 Apr, 2026 Editor invited by journal 01 Apr, 2026 Editor assigned by journal 30 Mar, 2026 Submission checks completed at journal 30 Mar, 2026 First submitted to journal 18 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9165736","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":634407429,"identity":"84492d53-9ec0-45b6-bea6-29bdc95eecc6","order_by":0,"name":"Batoul 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Hospital","correspondingAuthor":false,"prefix":"","firstName":"Sarab","middleName":"","lastName":"Agha","suffix":""}],"badges":[],"createdAt":"2026-03-19 06:38:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9165736/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9165736/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108837760,"identity":"7129f9c5-5aaf-4e4e-a301-722755ddb33c","added_by":"auto","created_at":"2026-05-09 00:17:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":728457,"visible":true,"origin":"","legend":"\u003cp\u003eCoronal (a) and axial (b) CT images of the posterior fossa mass demonstrating a well-circumscribed lesion with focal hyperdense areas, associated with obstructive hydrocephalus.\u003c/p\u003e","description":"","filename":"Figure1a.png","url":"https://assets-eu.researchsquare.com/files/rs-9165736/v1/fc97d34447398ba746481578.png"},{"id":109067562,"identity":"f61c9453-fe2b-4110-93fc-41a1c7173680","added_by":"auto","created_at":"2026-05-12 09:56:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":10651661,"visible":true,"origin":"","legend":"\u003cp\u003eH\u0026amp;E (×200) photomicrograph showing ependymal rosettes on the left with an adjacent focus of chondro-osseous metaplasia on the right.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-9165736/v1/6b46f5bad528d4827870997d.png"},{"id":108837761,"identity":"7dfb585d-8b7b-43ed-aadc-d519eb702632","added_by":"auto","created_at":"2026-05-09 00:17:36","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":9718072,"visible":true,"origin":"","legend":"\u003cp\u003eH\u0026amp;E (×40) photomicrograph showing multiple foci of osseous metaplasia within the ependymal neoplasm.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-9165736/v1/a15fe897c28973199dfdf3d1.png"},{"id":109069199,"identity":"398207d2-b77f-4b1a-9593-a4358a06829f","added_by":"auto","created_at":"2026-05-12 10:21:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":28980992,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9165736/v1/358ca003-fcda-4b14-ba90-4775b500c690.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Posterior Fossa Ependymoma with Chondro-Osseous Metaplasia in a Child: A Rare Case Report","fulltext":[{"header":"Background","content":"\u003cp\u003eEpendymomas are rare neuroepithelial tumors of the central nervous system, representing only 1.6\u0026ndash;1.8% of primary CNS neoplasms. They arise through oncogenetic alterations in tumor cells that promote ependymal differentiation. Typically, these tumors are well-circumscribed and originate from ependymal cells lining the ventricular system and the central canal of the spinal cord.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eApproximately half of all ependymomas occur in children, most often in the posterior fossa, making them the second most common solid brain tumor in the pediatric population after medulloblastoma. In children aged 1\u0026ndash;14 years, ependymomas account for about 5.7% of all diagnosed CNS tumors, with an estimated annual incidence of 0.30 per 100,000 individuals. The incidence is reported to be higher in males.[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eEpendymomas demonstrate a bimodal age distribution. The first peak occurs in childhood, with a mean age of presentation around 4 years, and these tumors most often arise intracranially, predominantly in the posterior fossa, followed by supratentorial sites. A second peak is seen in adults, typically between 20 and 40 years of age, where ependymomas usually present as intramedullary spinal tumors [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eAccording to earlier WHO grading schemes, ependymomas were divided into three categories: myxopapillary (Grade I), conventional (Grade II), and anaplastic (Grade III). However, the 2021 WHO Classification of CNS Tumors (CNS5) has revised this approach, emphasizing molecularly defined subgroups and reclassifying myxopapillary ependymoma as Grade II. Current diagnostic practice integrates both histological features and molecular markers, with supratentorial, posterior fossa, and spinal ependymomas now further stratified by genetic alterations such as ZFTA and YAP1 fusions, or MYCN amplification.[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e][\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eA survey of the English language literature has identified approximately 15 documented cases of ependymomas exhibiting chondroosseous metaplasia. These rare histopathological patterns account for only about 0.5% of all diagnosed ependymomas. The occurrence of cartilaginous or osseous differentiation within gliomas is exceedingly uncommon and has been most often recognized in fourth ventricular ependymomas and midline astrocytomas.[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e"},{"header":"Case Presentation","content":"\u003cp\u003eA 4-year-old female was admitted with a history of severe headache, often awakening her from sleep. The headache was persistent and unresponsive to analgesics. Over time, she developed progressive gait disturbance, imbalance, and dizziness.\u003c/p\u003e \u003cp\u003eOn neurological examination, fingertonose testing revealed dysmetria, consistent with cerebellar dysfunction. Her gait was broad-based, and she exhibited medial strabismus (esotropia). The Babinski sign was negative, suggesting no upper motor neuron involvement. There were no clinical signs of meningeal irritation or increased intracranial pressure. However, fundoscopy revealed bilateral papilledema, confirming raised intracranial pressure at the optic discs.\u003c/p\u003e \u003cp\u003eRadiological evaluation with CT and MRI demonstrated a posterior fossa mass extending to the right side, compressing the brainstem and associated with ventricular dilatation consistent with obstructive hydrocephalus (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eHistopathological Findings:\u003c/p\u003e \u003cp\u003eAn excisional biopsy was performed on the posterior fossa mass. The specimen was received in two containers, the first measuring 4.5 \u0026times; 3 \u0026times; 0.7 cm and the second measuring 6.5 \u0026times; 5 \u0026times; 1.3 cm.\u003c/p\u003e \u003cp\u003eMicroscopic examination demonstrated monomorphic cells with clear cytoplasm, fine nuclear chromatin, and inconspicuous nucleoli. The tumor cells exhibited fibrillary cytoplasmic processes that condensed in a collar like fashion around stromal blood vessels, forming perivascular pseudorosettes and occasional true rosettes (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Areas of dystrophic calcification were identified, along with foci of chondro-osseous metaplasia (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Importantly, no tumor necrosis was observed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBased on these findings, the lesion was concluded to represent an ependymoma (WHO Grade II), excised from the posterior fossa. Ancillary studies are pending, with EMA and Ki67 immunostains currently in processing.\u003c/p\u003e \u003cp\u003ePostoperative Course:\u003c/p\u003e \u003cp\u003eFollowing excisional biopsy, the patient developed clear esotropia and peripheral facial nerve palsy. Pupils remained equal and reactive. Cardiovascular and respiratory examinations were normal, with a full bounding pulse and unremarkable auscultation. The abdomen was soft, with palpable hepatomegaly. No seizures or vomiting were observed. A vesicular clustered rash on an erythematous base was noted over the right thigh and upper left gluteal region, consistent with herpes simplex infection.\u003c/p\u003e \u003cp\u003eThe patient was subsequently administered appropriate medications tailored to these findings. After treatment, she demonstrated improvement in her general condition and neurological status.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eEpendymomas are neuroepithelial tumors that develop from ependymal cells lining the cerebral ventricles. Their incidence ranges from 0.29 to 0.6 per 100,000 according to the Central Brain Tumor Registry of the USA. These tumors comprise between 1.6 and 1.8 of all primary CNS tumors, with higher incidence among children, and show slightly male predominance [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Cartilaginous metaplasia with or without bone formation is an exceptionally rare finding in ependymomas.[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Because of its rarity, its development and impact on prognosis are not clear yet.\u003c/p\u003e \u003cp\u003eFew theories have tried to explain the mechanism behind the chondro-osseous metaplasia. The most accepted theory suggests that these changes arise from metaplastic transformation of neoplastic glial or mesenchymal tissue. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] Another theory proposes that glial tumor cells may produce a material that is similar to the basement membrane which can condense and transform into mesenchymal tissue.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] G\u0026uuml;zey et al. suggested that the cartilage found in ependymoma case, might have developed from a transformation of the neuroepithelial cells to mesenchymal cells, as the cartilaginous tissue showed no fibrous capsule and immunoreacted positively to glial fibrillary acidic protein (GFAP) antibody [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Despite the proposed theories, the exact etiopathogenesis of these metaplastic change sin ependymomas remains unclear, because of the rarity of this histopathological finding.\u003c/p\u003e \u003cp\u003eWang et al. reported that ependymomas with cartilaginous metaplasia may be associated with a worse prognosis despite aggressive therapy. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] In contrast, Gessi et al. performed a case series of 13 rare histological ependymoma variants including four patients with cartilaginous-osseous ependymoma, and they could not identify an association between the tumor grade and the presence of chondro-osseous metaplasia.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] These conflicting findings could be due to the small number of reported cases, histological diversity and tumor grade, location and extent of tumor resection. As a result, the effect of this metaplasia on tumor prognosis is poorly understood.\u003c/p\u003e \u003cp\u003eAccording to the 2021 WHO classifications of CNS tumors, diagnosis of ependymomas now depends on a combination of histopathological and molecular findings as well as anatomic tumor location. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] This updated classification includes supratentorial ependymomas that are positive for ZEFTA fusion; supratentorial ependymomas positive for YAP1 fusion; posterior fossa ependymomas of group A and group B; as well as spinal ependymomas with MYCN amplification. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] In the present case the tumor was classified as WHO Grade II based on histopathological features, however, molecular testing could not be performed.\u003c/p\u003e \u003cp\u003eManagement of Ependymomas includes gross total resection with or without adjuvant radiotherapy.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] Previously reported cases in the literature are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, including the case reported by Bannykh et al. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Most reported cases are among children and show a predilection for the posterior fossa. Several cases with high grade tumor are associated with poor prognosis. In contrast, the present case shows favorable short-term outcome with no recurrence at 3 months follow-up.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePreviously reported cases of ependymoma with cartilaginous-osseous metaplasia\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFirst author\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGender\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eHistology\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eWHO grade\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eFollow-up and outcome\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWang X⁷\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFourth ventricle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEpendymoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eDeath at 18 months\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMridha AR\u0026sup1;⁰\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLeft cerebellopontine angle cistern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnaplastic\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNot available\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eGessi M⁸\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFourth ventricle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnaplastic\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNot available\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFourth ventricle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEpendymoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNot available\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFourth ventricle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSubependymoma/ Ependymoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNot available\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBannykh S\u0026sup1;\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLeft frontal lobe\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnaplastic\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eDeath at 6 months\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAlkhaibary A\u0026sup2;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFourth ventricle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnaplastic\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNo recurrence at 2 years\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShaivy M\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRight cerebellopontine angle cistern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePosterior fossa ependymoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eDeath at 9 months post-surgical excision\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePresent case\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFourth ventricle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEpendymoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNo recurrence at 4 months\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eThis table summarizes all published cases of ependymomas presenting with chondro‑osseous metaplasia, including patient age, gender, tumor location, histological type, WHO grade, and follow-up outcomes. Abbreviations: F, female; M, male; WHO, World Health Organization; NR, not reported. All tumors were confirmed by histopathology, and follow-up periods are indicated where available. Superscript numbers correspond to references in the manuscript.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis case describes a posterior fossa ependymoma with chondro-osseous metaplasia. Reporting more cases with long-term follow-up and thorough examination is crucial to improve understanding of its pathogenesis and prognostic significance.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCNS \u0026ndash; Central nervous system\u003c/p\u003e\n\u003cp\u003eCT \u0026ndash; Computed tomography\u003c/p\u003e\n\u003cp\u003eEMA \u0026ndash; Epithelial membrane antigen\u003c/p\u003e\n\u003cp\u003eGFAP \u0026ndash; Glial fibrillary acidic protein\u003c/p\u003e\n\u003cp\u003eMRI \u0026ndash; Magnetic resonance imaging\u003c/p\u003e\n\u003cp\u003eWHO \u0026ndash; World Health Organization\u003c/p\u003e\n\u003cp\u003eCNS5 \u0026ndash; 2021 World Health Organization Classification of Tumors of the Central Nervous System\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003eThe study was conducted in accordance with the Declaration of Helsinki. Ethical approval was obtained from the Ethics Committee of Aleppo University Hospital, Syria. Written informed consent was obtained from the patient\u0026rsquo;s legal guardian for participation in this case report.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003e Written informed consent was obtained from the patient\u0026rsquo;s legal guardian for publication of this case report and accompanying images. A copy of the consent form is available for review by the Editor-in-Chief.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eClinical trial number\u003c/h2\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eSA supervised and helped in writing the manuscript.BA, MN, KA and AA wrote the manuscript. KA performed histopathological examination. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe would like to acknowledge the use of ChatGPT, for its assistance in enhancing the language.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMalik S, Samanta SS, Kolte S. Posterior fossa ependymoma in a child with extensive chondro-osseous metaplasia occurring at cerebellopontine angle and masquerading as a vestibular schwannoma: an exceptionally rare clinicopathological manifestation with review of literature. J Neurol Surg Rep. 2024;85(3):e132\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1055/a-2372-6701\u003c/span\u003e\u003cspan address=\"10.1055/a-2372-6701\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlkhaibary A, AlSufiani F, Alassiri AH, Almuntashri M, Al Qutub ST. Chondro-osseous metaplasia in ependymoma: a rare histopathological finding. Case Rep Pathol. 2020;2020:1528698. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1155/2020/1528698\u003c/span\u003e\u003cspan address=\"10.1155/2020/1528698\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLouis DN, Perry A, Reifenberger G, von Deimling A, Figarella-Branger D, Cavenee WK, et al. The 2016 World Health Organization classification of tumors of the central nervous system: a summary. Acta Neuropathol. 2016;131(6):803\u0026ndash;20. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00401-016-1545-1\u003c/span\u003e\u003cspan address=\"10.1007/s00401-016-1545-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLouis DN, Perry A, Wesseling P, Brat DJ, Cree IA, Figarella-Branger D, et al. The 2021 WHO classification of tumors of the central nervous system: a summary. Neuro Oncol. 2021;23(8):1231\u0026ndash;51. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/neuonc/noab106\u003c/span\u003e\u003cspan address=\"10.1093/neuonc/noab106\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOrmond DR, Hadley C, Gressot LV. Current management of adult ependymoma. Curr Treat Options Oncol. 2022;23(9):1185\u0026ndash;99. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11912-022-01260-w\u003c/span\u003e\u003cspan address=\"10.1007/s11912-022-01260-w\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChakraborti S, Govindan A, Alapatt JP, Radhakrishnan M, Santosh V. 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Anaplastic ependymoma with cartilaginous and osseous metaplasia: report of a rare case and review of literature. J Neurooncol. 2007;82(1):75\u0026ndash;80. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s11060-006-9239-5\u003c/span\u003e\u003cspan address=\"10.1007/s11060-006-9239-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBannykh S, Baehring JM. Images in neuro-oncology: rapid development of osseous and chondrous metaplasia in recurrent anaplastic ependymoma. J Neurooncol. 2007;81(3):257\u0026ndash;8. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s11060-006-9225-y\u003c/span\u003e\u003cspan address=\"10.1007/s11060-006-9225-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-neurology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nurl","sideBox":"Learn more about [BMC Neurology](http://bmcneurol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/nurl","title":"BMC Neurology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Ependymoma, Chondro-osseous metaplasia, Posterior fossa tumor, Pediatric brain tumor, Histopathological variant, Central nervous system neoplasm, Case report","lastPublishedDoi":"10.21203/rs.3.rs-9165736/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9165736/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEpendymomas are glial tumors characterized by perivascular pseudorosettes. The presence of chondro-osseous metaplasia in these tumors is extremely rare with fewer than 10 cases reported in the literature.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCase presentation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe report a 4-year-old girl who presented with headaches, progressive gait disturbance and dizziness. Neurological examination revealed cerebellar signs and bilateral papilledema. MRI showed a posterior fossa mass with obstructive hydrocephalus. Histopathological examination confirmed a WHO Grade II ependymoma with areas of chondro-osseous metaplasia. At 4-months follow-up, there was no recurrence.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe etiology and prognosis of these histopathological variants remain unclear due to the limited number of reported cases. This case highlights the clinical presentation, pathological characteristics, and outcome of an ependymoma with chondro-osseous metaplasia.\u003c/p\u003e","manuscriptTitle":"Posterior Fossa Ependymoma with Chondro-Osseous Metaplasia in a Child: A Rare Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-09 00:17:32","doi":"10.21203/rs.3.rs-9165736/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-05-15T06:51:07+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-11T15:05:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"274997154170799680001787499781538758278","date":"2026-05-05T08:11:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"220363236710736080776001272664974243396","date":"2026-05-04T17:17:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"242078145524891811656333450902175813101","date":"2026-04-26T16:50:55+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-24T11:38:33+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-01T09:41:30+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-30T07:26:49+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-30T07:26:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Neurology","date":"2026-03-19T02:00:17+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-neurology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nurl","sideBox":"Learn more about [BMC Neurology](http://bmcneurol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/nurl","title":"BMC Neurology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0f035fa4-a83b-403a-90e9-bab8404702eb","owner":[],"postedDate":"May 9th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-15T06:51:07+00:00","index":73,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-11T15:05:00+00:00","index":72,"fulltext":""},{"type":"reviewerAgreed","content":"274997154170799680001787499781538758278","date":"2026-05-05T08:11:02+00:00","index":68,"fulltext":""},{"type":"reviewerAgreed","content":"220363236710736080776001272664974243396","date":"2026-05-04T17:17:54+00:00","index":63,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-09T00:17:32+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-09 00:17:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9165736","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9165736","identity":"rs-9165736","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}