IntroductionPleomorphic adenoma (PA) is the most common benign tumor
of the major salivary glands. It may also arise from minor salivary glands of the
upper aerodigestive tract. PA of the auditory canal is a rarity. The earlier
hypothesis that PA of the auditory canal originates from ectopic salivary gland
tissue has not yet been proven. Currently it is assumed that PA of the external
auditory canal originates from the myoepithelia of the local ceruminal glands. The
tumor is accordingly classified by the WHO as a ceruminal adenoma. The tendency to
recurrence and malignant transformation known from PA of the salivary glands has
also been described for PA of the auditory canal.
Case reportAn 81-year-old patient complained of a left-sided increase
of bilateral pre-existing hearing loss for several weeks. On the microscopy of the
ear the left auditory canal was almost completely closed by a smooth, rough
protrusion of the auditory canal floor. The pure-tone audiogram showed a
sensorineural hearing loss on the right and a combined hearing loss on the
left. Computed tomography of the petrous bone revealed a 5 mm soft tissue formation
without bony destruction obstructing the left auditory canal. The tumor was
completely resected by transmeatal approach in general anesthesia. Histological
work-up revealed a diagnosis of PA. Six weeks after surgery the ear canal appeared
completely re-epithelialised and wide.
ConclusionsPA is a very rare but important differential diagnosis of
tumors of the external auditory canal because of potential malignant transformation.
Therapy consists of complete excision with long-term follow-up because of the risk
of recurrence.
