CNS & pituitary tumors


Colloid cyst

Last author update: 1 February 2012
Last staff update: 29 July 2020

Copyright: 2002-2023,, Inc.

PubMed Search: Colloid cyst [title] CNS cyst

Eman Abdelzaher, M.D., Ph.D.
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Cite this page: Abdelzaher E. Colloid cyst. website. Accessed April 2nd, 2023.
Definition / general
  • Benign unilocular, epithelium lined, mucin filled cyst of third ventricle (eMedicine: Colloid Cysts)
  • Uncertain histogenesis, mostly of endodermal derivation
  • Usually adults (20 - 50 years), rare in children
  • Site, radiologic and pathologic features are distinctive so differential diagnosis may be limited
  • Anterior third ventricle near foramen of Monro
Clinical features
  • Due to its position, causes intermittent obstruction of CSF flow and headache is most common symptom
  • Sudden impaction causes transient lower limb paralysis (drop attacks) and may be fatal
  • May rupture and mimic abscess or ventriculitis unless colloid is identified
Radiology description
  • Spherical nonenhancing discrete lesion at anterior third ventricle
Radiology images

Images hosted on other servers:

Various images

Case reports
Gross description
  • 1 cm or larger
  • Round, unilocular with thin glistening wall
  • Cyst filled with turbid and viscid material that solidifies after fixation
Gross images

Images hosted on other servers:

Obstruction of foramen of Monro by gelatinous cyst

Microscopic (histologic) description
  • Hypocellular fibrous wall lined by simple columnar epithelium with variable cilia or mucin (resembles bronchial epithelium); may be pseudostratified or flattened
  • Unlike Rathke cleft and enterogenous cysts, lining epithelium is not prone to squamous metaplasia
  • Fragments of normal choroid plexus are frequently attached to cyst
  • Cyst content may show ghosts of desquamated lining cells, eosinophilic filamentous material resembling actinomyces
  • In chronic lesions, a xanthogranulomatous reaction may occur
Positive stains
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