[Development of cholesteatoma in the middle ear ab statu nascendi].

The squamous epithelium and the granulating chronically inflamed mucosa of the middle ear are responsible for the development of a cholesteatoma. Squamous epithelium is stimulated to grow if it borders on granulation tissue, as in wound healing. Thus if granulation tissue forms in the tympanic membrane the basal membrane degenerates at circumscribed points and these matrix cells produce processes which grow in an atypical direction into the middle ear. The resulting mass of prickle cells acts as a foreign body and stimulates the growth of bone destroying soft tissue. This explains the posterior superior defect in the tympanic membrane.