Secondary cholesteatoma, an acquired open-typed cholesteatoma, is considered to be formed by disorderly migration of epidermis. The epidermis, which is activated by chronic inflammation, becomes to extend from the manubrium of the malleus at the center of a perforation of the tympanic membrane. The epidermis then passes along the inner surface of the tympanic membrane through the edge of perforation of an opentyped cholesteatoma. We reported 3 cases of secondary cholesteatoma. Patients 1 and 2 showed common characteristics of secondary cholesteatoma that have been reported: a large perforation of the tympanic membrane, long-term inflammation of the middle ear and an open-typed cholesteatoma extended from the manubrium of the malleus to the inner surface of the tympanic membrane. However, in patients 3 with a traumatic small perforation of the tympanic membrane, his secondary cholesteatoma seemed to be formed under a specific condition of severe persistent inflammation due to MRSA. After tympanoplasty, it is suggested that the epidermis folded on the inner surface of the tympanic membrane at the edged of the perforation was activated by MRSA inflammation and extended to form an open-typed cholesteatoma.
