Middle ear cholesteatoma is a cystic structure that is not a true tumor. They are usually classified according to their pathogenesis as congenital cholesteatoma, acquired primary cholesteatoma, and acquired secondary cholesteatoma. Patients with congenital cholesteatoma have a normal tympanic membrane, so it is often difficult to be detected in the early stages until hearing loss occurs, and the diagnosis is basically confirmed if an examination reveals a white mass shadow behind the tympanic membrane. Acquired primary cholesteatoma is the most common. Patients often have a history of long-term obstruction of the eustachian tube during childhood, and due to the formation of negative pressure in the upper tympanic chamber of the middle ear, this eventually leads to pouch-like invagination of the relaxed part of the tympanic membrane, and the shedding of epithelium gradually collects in the invaginated pouch, eventually forming a cholesteatoma; the clinical presentation of this type of patient varies greatly, and some may have a history of ear discharge and hearing loss, but some patients may not have any obvious Some patients may have a history of ear discharge and hearing loss, but others may have no symptoms at all. Acquired secondary cholesteatoma often occurs in patients with marginal perforation of the tympanic membrane due to the growth of the epithelium of the external auditory canal along the edge of the perforation into the tympanic cavity, and is characterized by early onset of symptoms, including ear pus and hearing loss; acquired secondary cholesteatoma can also occur as a result of ear trauma and surgery. Cholesteatoma consists of a cystic wall with multiple layers of squamous epithelium and a cystic content consisting of exfoliated squamous epithelium and keratinized material. Although cholesteatoma is not a true tumor, it has characteristics similar to those of a tumor, such as gradual growth, destruction of bone, residual and recurrence. Because of these characteristics, cholesteatoma can lead to destruction of the auditory tuberosities and even certain serious complications such as facial paralysis, labyrinthitis, meningitis and brain abscess. Therefore, the principle of treatment for cholesteatoma is to operate as soon as it is detected.