Cholesteatoma is a unique disease of the ear in which a skin cyst grows into the middle ear and mastoid. While not cancerous, the cyst can erode tissue and cause destruction of the ear. The majority of patients don’t realize a cholesteatoma is present. Cholesteatoma is not often painful, however, infection may occassionally occur, causing pain and swelling behind the ear. A cholesteatoma is detected only by examining the ear and finding the disease.