A cholesteatoma is an abnormal skin growth in the middle ear behind the eardrum. Repeated infections can allow skin to build up in the middle ear. The growth, however, is not cancerous.

Cholesteatomas often develop as cysts or pouches that shed layers of old skin inside the middle ear. Over time, the cholesteatoma can grow and damage the surrounding delicate bones of the middle ear. This can lead to hearing loss that surgery can often improve.