Cholesteatoma is a benign growth that consists of a buildup of squamous epithelial skin cells that grow into the middle ear and mastoid bone. These are benign conditions and are not tumors but can grow with time causing problems because of erosion of the bones inside and surrounding the ear and the base of the skull. These lesions generally grow slowly as the more and more layers of old skin cells and their secretions are deposited within the bone of the ear and skull base. The destruction of the bones of the middle ear will often lead to hearing loss and can rarely extend into the skull base where they can exert pressure onto the brain.
Cholesteatoma usually occur because of poor eustachian tube function and repeated infections in the middle ear. The eustachian tube allows air from the ear to communicate to the nose. When the eustachian tube is blocked because of allergy, anatomic predisposition, or infections a small vacuum can develop which brings in the epithelial skin cells that lead to formation of a Cholesteatoma.