Cholesteatoma of the middle ear in human patients. An ultrastructural study.

The structure of middle ear cholesteatoma obtained at surgical interventions in 12 patients was investigated by light and electron microscopy. Keratinizing squamous epithelium with underlying granulomatous, partly necrotic tissue showing signs of an acute or chronic inflammatory reaction was observed. Cholesterol clefts were only observed in two specimens in which a chronic hemorrhage was present. It is proposed that a cholesteatoma starts by immigration of epidermal tissue from the tympanic membrane. Destruction of the middle ear components and of the neighboring osseous walls results from invasion of squamous epithelium, underlying necrotizing connective tissue, and keratin.