[Origin of acquired middle ear cholesteatoma]

The acquired cholesteatoma of the middle ear develops from shifted ectodermal epithelium. The transposition takes place in a typical way by ingrowth from canal wall or tympanic membrane lining similar to wound healing. A precondition is a perforative chronic otitis media. In our terminology, an atypical shift of epithelium is a retraction pocket over poorly aerated parts of the tympanum. The matrix, activated by supporting connective tissue, follows the same tissue kinetic principles as the epidermis. In case of cholesteatoma we have a discrepancy of vertical (keratinisation) and horizontal (migration) regeneration, creating a keratin-cystlike structure. The cells of Langerhans, which control epidermal growth and type of keratinisation, seem to play an important role. Their density is low in stressregions of the epidermis and in the active matrix of the cholesteatoma.