Middle ear, inner ear and temporal bone tumors - benign / nonneoplastic

Author: Nat Pernick, M.D. (see Authors page)

Revised: 23 February 2018, last major update October 2013

Copyright: (c) 2002-2018, PathologyOutlines.com, Inc.

PubMed Search: Cholesteatoma [title] ear pathology review[ptyp]

Cite this page: Pernick, N. Cholesteatoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/earcholesteatoma.html. Accessed May 22nd, 2018.
Definition / general
  • Also called keratoma (more accurate term), epidermal inclusion cyst of middle ear
  • Stratified squamous epithelium that forms saclike accumulation of keratin within middle ear space
  • Usually men, ages 20s to 30s
  • May be (a) congenital (squamous epithelium is trapped within temporal bone during embryogenesis; tympanic membranes are intact; no history of infections), (b) primary acquired (retraction of tympanic membrane), (c) secondary acquired (due to injury to tympanic membrane)
  • May cause progressive bone erosion of ossicles and surrounding bone but is not neoplastic; incomplete excision may lead to widespread bone destruction
  • Damage apparently is due to associated inflammation and proteolytic enzymes, not pressure from tumor mass (Mod Pathol 2001;14:1226)
  • Aural polyps composed of granulation tissue and with keratin flakes or masses are usually associated with underlying cholesteatoma (J Clin Pathol 1989;42:460)
Prognostic factors
  • Presence of papillary epithelial hyperplasia and marked koilocytosis is associated with aggressive disease and HPV (Med Sci Monit 2006;12:CR368)
  • Complete excision of all components
Gross description
  • Cystic, white masses of varying size with creamy or waxy granular material
Gross images

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Yellow white waxy material

Microscopic (histologic) description
  • Keratinized stratified squamous epithelium (required for diagnosis) with granulation tissue and keratin debris
  • Chronic inflammatory infiltrate, cholesterol clefts, foreign body giant cell granulomas, hemosiderin
  • No dysplasia
Microscopic (histologic) images

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Squamous epithelium with keratin debris

Differential diagnosis