A cholesteatoma is a skin cyst that occurs in the middle ear or mastoid process. Cholesteatomas can be congenital, but most are complicated by chronic infection of the middle ear. Malfunction of the eustachian tube leads to negative pressure in the middle ear, causing invagination of the loose part of the tympanic membrane and the formation of invagination pockets. The collection and expansion of desulfated epithelium in the invagination pockets further destroys the surrounding bone and infections, causing hearing loss, balance disorders, and facial paralysis. Common symptoms, signs and examinations: 1. dizziness; 2. ear pus and odor; 3. hearing loss; 4. perforation of the flaccid part and pea-like material; 5. audiological examination to understand hearing damage; 6. CT to understand the extent of the lesion and structural destruction of the middle ear. Treatment: Surgery is usually required. The surgical options range from cleaning of the invaginated pouch, opening of the superior tympanic chamber, complete mastoidectomy, modified mastoidectomy, or radical mastoidectomy, with the surgical procedure and scope determined by the extent of the lesion. Prognosis: Without surgical excision, cholesteatoma can grow. Follow-up may be required after completion surgery to detect early recurrence of the lesion; open surgery may require periodic cleaning of the operative cavity. If the cholesteatoma assists, reoperation will be required. Conditions requiring medical attention: Promptly seek the help of an otologist for ear symptoms such as ear pain, drainage, dizziness, hearing loss, tinnitus, and facial paralysis. Prevention: Aggressive and thorough treatment of chronic ear infections and nasal disorders may prevent the development of some cholesteatomas.