Monarch Disease Ontology identifier MONDO_0006533 (cholesteatoma of middle ear) is a non-neoplastic lesion characterized by the proliferation of keratinizing squamous epithelium in the middle ear that results in the accumulation of keratin and cells. It is usually caused by repeated infections. If left untreated, it may increase in size and destroy the adjacent delicate bones of the middle ear. Also known as: Epidermosis of ear, Epidermosis of middle ear, cholesteatoma (disease) of middle ear, cholesteatoma of middle ear and mastoid, cholesteatoma of middle ear and/or mastoid, cholesteatoma of the middle ear, middle ear cholesteatoma, middle ear cholesteatoma (disease).