Subependymoma

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Sujit Routray, M.D. [2]

Synonyms and Keywords: Subependymomas; Subependymal astrocytoma; Subependymal astrocytomas

Overview

Subependymoma is a type of brain tumor; specifically, it is a rare form of ependymal tumors.[1] Subependymoma is a benign (WHO grade I) tumor, which is slow growing and non-invasive.[2]

Pathophysiology

Pathogenesis

  • Subependymoma arises from subependymal glial cells, although it can also arise from astrocytes from the subependymal plate, ependymal cells, and mixed ependymal and astrocytic cells.[3]

Gross Pathology

  • Subependymoma is most commonly seen in the fourth ventricle, but can arise anywhere where there is ependyma. The distribution in the ventricular system is as follows:[4]
  • On gross pathology, subependymoma is characterized by a small, white to grey, firm, well circumscribed, solid, avascular mass attached to the ventricular wall by a narrow pedicle.[3]

Microscopic Pathology

  • On microscopic histopathological analysis, subependymoma is characterized by microcystic spaces and bland appearing cells without appreciable nuclear atypia or mitoses. The nuclei tend to form clusters. No high grade features (mitoses, Ki-67 / MIBI index > 1.5%, necrosis) are present. Loose pseudorosettes are observed.[4]

Immunohistochemistry

  • Subependymoma is demonstrated by positivity to tumor marker such as GFAP.[4]

Differentiating Subependymoma from other Diseases

Epidemiology and Demographics

Prevalence

  • Subependymoma constitutes approximately 1% of all intracranial tumors.[3]

Age

  • Subependymoma is a rare disease that tends to affect middle-aged adults and the elderly population (typically 5th to 6th decades).[6]

Gender

  • Males are more commonly affected with subependymoma than females. The male to female ratio is approximately 2.3 to 1.[6]

Natural History, Complications and Prognosis

Natural History

Complications

Prognosis

  • The prognosis of subependymoma is excellent wih complete excision of the tumor.[3]

History and Symptoms

History

  • When evaluating a patient for subependymoma, you should take a detailed history of the presenting symptom (onset, duration, and progression), other associated symptoms, and a thorough family and past medical history review.

Symptoms

  • Typically patients of subependymoma are asymptomatic and small lesions are discovered incidentally.
  • Symptoms of subependymoma include:[8]

CT

  • Head CT scan is helpful in the diagnosis of subependymoma. On CT scan, subependymoma is characterized by:[9]
  • Iso- and hypodense intraventricular mass
  • Positive mass effect
  • No enhancement
  • If large, it may have cystic or even calcific components
  • No vasogenic edema

MRI

  • Brain MRI is helpful in the diagnosis of subependymoma. On MRI, subependymoma is characterized by:
MRI component Findings

T1 weighted image

  • Iso - hypointense compared to white matter
  • Homogeneous but may be heterogeneous in larger lesions

T2 weighted image

  • Hyperintense compared to adjacent white and grey matter
  • Heterogeneity may be seen in larger lesions, with susceptibility related signal drop out due to calcifications
  • No adjacent parenchymal edema (as no brain invasion is present)

T1 weighted image with contrast

  • Little or no enhancement

Biopsy

  • Biopsy of the subependymoma tumor, taken through a needle during a simple surgical procedure, helps to confirm the diagnosis.[10]

Treatment

References

  1. Subependymoma. Wikipedia 2016. https://en.wikipedia.org/wiki/Subependymoma. Accessed on January 12, 2016
  2. Subependymoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/subependymoma. Accessed on January 12, 2016
  3. 3.0 3.1 3.2 3.3 Saad AF, Bidiwala SB, Layton KF, Snipes GJ, Opatowsky MJ (2013). "Fourth ventricular subependymoma presenting as worsening headache.". Proc (Bayl Univ Med Cent). 26 (1): 52–4. PMC 3523772Freely accessible. PMID 23382616. 
  4. 4.0 4.1 4.2 Pathology of subependymoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/subependymoma. Accessed on January 12, 2016
  5. Intraventricular neoplasms and lesions. Dr Henry Knipe and Dr Vinod G Maller et al. Radiopaedia 2016. http://radiopaedia.org/articles/intraventricular-neoplasms-and-lesions. Accessed on January 12, 2016
  6. 6.0 6.1 Epidemiology of subependymoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/subependymoma. Accessed on January 12, 2016
  7. 7.0 7.1 Clinical presentation of subependymoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/subependymoma. Accessed on January 12, 2016
  8. KE, Changshu. "Subependymoma: a case report and the review of literatures". doi:10.3969/j.issn.1672-6731.2011.01.021. 
  9. Radiographic features of subependymoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/subependymoma. Accessed on January 12, 2016
  10. Diagnosis of subependymoma. Wikipedia 2016. https://en.wikipedia.org/wiki/Subependymoma. Accessed on January 8, 2016

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