Rare Epidermoid Cyst in Bony External Auditory Canal with Labyrinthine Fistula

Abstract The presence of an epidermoid cyst in the bony wall of the external auditory canal (EAC) is an exceedingly rare condition, often necessitating surgical intervention due to meatal obstruction. A 13-year-old girl presented with a mass in the right EAC, causing obliteration, bony destruction, and profound sensorineural hearing loss. Temporal bone computed tomography revealed a labyrinthine fistula resulting from soft-tissue density eroding the cochlear promontory’s bony wall. The 8.6 mm × 6.8 mm mass was excised through a postaural approach under general anesthesia, followed by tympanoplasty with cortical mastoidectomy. Histopathological examination confirmed the presence of an epidermoid cyst in the bony EAC. Postoperatively, there was a modest improvement in hearing. Despite the rarity of such cases, considering epidermoid cysts in EAC mass evaluations is crucial to mitigate the potential risk of malignant transformation.