External auditory canal cholesteatoma is a cystic mass formed by skin desquamation of the external auditory canal, accumulation of cholesterol crystals, and epithelial encapsulation. It is not a true tumor, so it is also known as an obstructive keratosis or epidermolysis bullosa of the external auditory canal. The inner layer of the cystic mass is a compound squamous epithelium (including basal layer, granular layer, spiny cell layer, and keratinized layer), and the outer layer of the cyst, i.e., the stroma, is a layer of fibrous tissue of varying thickness, which is closely connected to the surrounding adjacent tissues. It is most common in middle-aged and elderly people, with no significant difference in incidence between men and women. Cholesteatoma of the external auditory canal can be divided into two types: primary and secondary. The cause of primary external auditory canal cholesteatoma is still unclear, but it may be related to the long-term chronic inflammation of the external auditory canal and its relative narrowness. The main symptoms include ear stuffiness, hearing loss, and ear drainage in case of infection. It is distinguished from cerumen embolism because of its destructive nature. Early external auditory canal cholesteatomas are small and can be cleaned regularly in an outpatient setting and treated locally. Larger external auditory canal cholesteatomas may be associated with destruction of the surrounding bone, invasion of the middle ear mastoid and even the facial nerve, and require hospitalization. Secondary cholesteatoma of the external auditory canal usually has a history of trauma to the ear, followed by narrowing or atresia of the external auditory canal and secondary cholesteatoma, which must be treated as soon as possible.