Clinical characteristics and treatment outcome of adenoid cystic carcinoma in the external auditory canal

Background: This study reviewed the clinical manifestations, pathological findings, and treatment outcomes of adenoid cystic carcinoma (ACC) in the external auditory canal (EAC). Methods: This was a retrospective review of 12 patients with a diagnosis of ACC in the EAC seen in a single institution over a 30-year period. Data on the demographics, clinical presentation, treatment strategy, and outcome, as well as the pathological features of ACC, were reviewed and analyzed. Results: The male-to-female ratio was 1:3 and the mean patient age was 55.9 years. The most common clinical presentation was otalgia (75%). Ten patients underwent surgical interventions, including radical mastoidectomy in five patients, wide excision in three, and lateral temporal bone resection in two. Adjuvant radiotherapy or concurrent chemoradiotherapy (CCRT) was performed in case of incomplete resection. Two patients underwent non-surgical treatments: radiotherapy in one and CCRT in the other. Microscopic perineural invasion was not associated with otalgia or histological subtype. The mean follow-up period was 84.6 months. Local recurrence occurred in 33% of patients. One-quarter of patients had distant metastasis, and all had lung metastasis. The 5-year overall survival rate for these patients was 82.5%. Conclusion: EAC ACC should be included in the differential diagnosis when a patient presents with otalgia and a mass in EAC for more than 6 months, particularly if the patient is a middle-aged female. Otalgia might not be associated with perineural invasion or histological subtype. The lung is the most common site of distant metastasis in patients with EAC ACC. Further studies should determine the optimal treatment protocol for this rare malignancy.