Cholesteatoma is the skin growth (skin cyst) in the middle ear and mastoid. There are 2 types of cholesteatoma, “acquired” which occurs due to repeated ear infections and “congenital” which is present since birth. When squamous epithelium (skin layer) gets trapped behind the eardrum in the middle ear or mastoid then there is no where for it to escape as it enlarges and leads to cholesteatoma. Cholesteatoma usually grows very slowly, and it causes symptoms as it compresses and erodes surrounding bone and other structures.