Congenital External Auditory Canal Cholesteatoma Resected by a Transcanal Endoscopic Approach.

Objective: To describe the first case of congenital external auditory canal cholesteatoma resected via a transcanal endoscopic approach and describe the possible pathologenesis of cholesteatoma.

Patient: A 2-year-old female patient presented with a cholesteatoma that extended from the floor of the external auditory bony canal to the inferior quadrant of her right tympanic membrane.

Intervention: Otological examinations and computed tomography were performed. The cholesteatoma was resected using a transcanal endoscopic approach.

Results: Pathologic examination confirmed the diagnosis of external auditory canal cholesteatoma. The patient's postoperative hearing was observed to be normal. Cholesteatoma did not recur during the 2-year follow-up period. Computed tomography scan revealed an isodense mass, partly surrounded by bony tissue, on the floor of the external auditory canal, outside of the inferior quadrant of an intact tympanic membrane. A minor malformation of the bony tissue, covering the inferiolateral surface of the cholesteatoma, was observed. The proposed mechanisms of pathogenesis are: 1) the embryonic developmental deficits of the meatal plug, during its differentiation into squamous epithelium, cause the arrest of ectodermal tissues, 2) a remnant of the squamous epithelium becomes trapped in the niche of the foramen tympanicum.

Conclusion: A rare case of congenital external auditory canal cholesteatoma, located on the inferior external auditory canal, was diagnosed and resected using a transcanal endoscopic approach. It was possibly caused by a minor anomaly of the first branchial cleft or by a remnant of the squamous epithelium trapped in the foramen tympanicum.