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Cholesteatoma results from the presence of keratinizing epithelium
within the middle ear. Acquired
cholesteatoma can occur as sequelae of otitis media.
Squamous epithelium of the external canal can enter the middle ear
through a perforation of the tympanic membrane or form a
cholesteatomatous sac from a retraction pocket.
The keratinizing epithelium continues to desquamate, within the
enclosed middle ear space, finally eroding bony structures.
The
histological characteristics of cholesteatoma include a keratinizing
epithelium with keratohyline granules, and exfoliated keratin.
There is an associated inflammatory response and a middle ear
effusion.
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This
64-year-old white male had bacterial meningitis. A cholesteatoma fills the space between the tympanic membrane
(TM) and a dehiscent facial nerve (FN).
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