What is a cholesteatoma?

• A. A noncancerous skin-filled cyst in the middle ear that can erode surrounding bones
• B. Malignant tumor in the ear canal
• C. Fluid-filled sac behind the tympanic membrane
• D. Chronic ear infection without complications

Answer: (A)

Cholesteatoma is a keratinizing squamous epithelium–derived lesion that forms a skin-filled sac in the middle ear and/or mastoid. It typically arises from a retraction pocket or tympanic membrane perforation and fills with desquamated keratin debris. Although it is not cancerous, it behaves destructively, slowly eroding surrounding bone such as the ossicles and the walls of the middle ear, and it can extend to involve the facial nerve or inner ear. This erosion leads to conductive hearing loss and other potential complications if not treated. It’s not a malignant tumor of the ear canal, nor simply a fluid-filled sac behind the tympanic membrane, nor just a chronic ear infection without complications—the defining feature is a destructive, keratin-filled lesion in the middle ear.