CNS tumor
Ependymal tumors
Ependymoma
Author: Eman Abdelzaher, M.D., Ph.D.
Topic Completed: 1 August 2012
Minor changes: 24 November 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Ependymoma [title] CNS
See also: Clear cell Papillary Tanycytic
Table of Contents
Definition / general | Epidemiology | Sites | Grading | Subtypes | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosis | Additional referencesCite this page: Abdelzaher E. Ependymoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/Cnstumorependymoma.html. Accessed January 24th, 2021.
Definition / general
- Slowly growing tumor of ependymal cells arising from walls of ventricles or spinal canal
- Exhibit glial (GFAP+) and epithelial (EMA+) differentiation
Epidemiology
- 3 - 9% of primary CNS tumors
- More common in children / young adults but all age groups are affected (1 month - 81 years)
- Infratentorial ependymomas more common in children; cause hydrocephalus from obstruction if in posterior fossa
- Spinal tumours more common in adults (30 - 40 years); better able to excise completely and generally better prognosis at this site
- Supratentorial ependymomas affect both children and adults
- No gender predilection
Sites
- Arise in ventricles (lined by ependyma) in cerebrum or brainstem, including spinal cord remnant of central canal
Grading
- WHO grade II
Radiology description
Neuroimaging:
- Well circumscribed lesions with variable enhancement
- May have cystic change (especially in supratentorial tumours), hemorrhage, calcification
Radiology images
Images hosted on other servers:
MRI: Ependymoma of fourth ventricle
Prognostic factors
- Poor prognosis due to CSF dissemination (average survival 4 years with surgery and radiation) and inability to excise completely (near pontine and medullary nuclei)
- Poor prognostic factors are radiologic residual disease after surgery; higher Ki67 indices ( > 20.5%, Am J Surg Pathol 2004;28:914)
- Poor prognostic factors for pediatric intracranial tumors are:
- Subtotal resection with p53+ or MIB+ > 5% or
- Complete resection with MIB > 15% in hypercellular areas (Mod Pathol 2003;16:980)
Case reports
- 13 year old girl and 52 year old man with melanotic ependymoma (Am J Surg Pathol 1990;14:729)
- 14 year old boys with giant cell ependymoma of filum terminale (Am J Surg Pathol 1996;20:1091)
- 31 year old woman with cauda equina tumor with features of ependymoma and paraganglioma (Hum Pathol 1992;23:835)
- 45 year old man with pigmented ependymoma with lipofuscin and neuromelanin production (Arch Pathol Lab Med 2003;127:872)
- 66 year old man with giant cell ependymoma of fourth ventricle (Case of the Week #208)
- 66 year old man with collision tumor with malignant triton tumor (Arch Pathol Lab Med 2001;125:1113)
Treatment
- Gross total removal, often difficult
Gross description
- Soft tan masses
- May have discrete margin from surrounding brain or spinal cord
- Grows exophytically into fourth ventricle
- Ependymomas can fill fourth ventricle and exit out through foramina of Luschka or Magendie (called plastic ependymomas)
Gross images
Images hosted on other servers:
Arising from floor of fourth ventricle
Microscopic (histologic) description
- Ependymomas have discrete interface with surrounding parenchyma
- Moderately cellular, composed of monomorphic cells with round / oval nuclei and salt and pepper chromatin
- No / rare mitoses are rare
- Key histological features are perivascular pseudorosettes and ependymal rosettes
- Other features include: areas of fibrillarity, regressive changes (myxoid degeneration, hemorrhage, calcifications, hyalinized vessels)
- Variable nonpalisading necrosis
- Cellular ependymoma: shows conspicuous cellularity without other properties of anaplasia (thus WHO grade II); pseudorosettes may be inconspicuous, and true ependymal rosettes may be absent (eMedicine: Ependymoma Pathology)
Ependymal rosettes and ependymal canals:
- Composed of columnar cells arranged around a central lumen
- Lumen may be round or oval, does not have a hypereosinophilic border
- True rosettes are diagnostic of ependymoma but not always present
Perivascular (pseudo) rosettes:
- Ependymal cell processes directed towards vessel wall, processes become thinner as they extend around blood vessel with formation of perivascular anuclear zones of GFAP+ fibrillary processes
- More common than ependymal rosettes in ependymoma but also present in glioma
Positive stains
- GFAP, S100, vimentin
- EMA (positive along luminal surface of ependymal rosettes or as dot-like cytoplasmic vacuoles representing microlumens)
- Rarely cytokeratin
Negative stains
- Most neuronal antigens; no reticulin or type IV staining fibrils in ependymoma aggregates
Electron microscopy description
- EM is necessary to differentiate ependymoma from glioma if rosettes not present
- Ependymoma has perivascular rosettes, abnormal cilia, intracytoplasmic lumina with variable microvilli and cilia, basal bodies, microvillous inclusions; perinuclear intracytoplasmic intermediate filaments, long junctional complexes
- No basement membrane found in aggregated ependymoma cells
Molecular / cytogenetics description
- #22 deletions in 30 - 70%; inactivation of NF2 or loss of expression of protein in 29 - 38% of spinal tumors
- Alterations in protein 4.1 family members is common
- Loss of protein 4.1B and 4.1R deletions more common in childhood, intracranial and anaplastic tumors
- Protein 4.1G deletions associated with more aggressive disease (Mod Pathol 2005;18:991, Mod Pathol 2002;15:526)
Differential diagnosis
- Glioma: no true rosettes, no cell - cell junctions, no intracytoplasmic microvilli lined lumina
