Two cases of adenoid cystic carcinoma of the external auditory canal

Auditory canal cancers are extremely rare and occur in only 1 per 1 million individuals. An external auditory canal carcinoma is the most common type of auditory canal cancer, accounting for approximately 0.2％ of all head and neck cancers. Histopathologically, squamous cell carcinoma is the most common type; other types include adenoid cystic carcinoma, basal cell carcinoma, malignant melanoma, and adenocarcinoma. Usually, adenoid cystic carcinoma shows relatively slow tumor growth, frequent local recurrence, distant metastasis, and resistance to radiotherapy and anticancer drug treatment. Therefore, surgery is the only therapeutic option for this histopathological cancer type, which is associated with poor prognosis. In this study, we report two cases of adenoid cystic carcinoma of the external auditory canal cartilage in patients who were successfully treated surgically. Case 1: An 81-year-old man was referred to our hospital for additional resection of an adenoid cystic carcinoma with positive margins after removal of a right ear canal mass at another hospital. General anesthesia was contraindicated in this patient with diminished respiratory function owing to a history of pulmonary tuberculosis; therefore, we performed partial temporal bone resection under local anesthesia. No local recurrence was observed 15 months postoperatively. Case 2: A 69-year-old man was referred to our hospital for comprehensive evaluation of persistent left ear pain. Biopsy findings revealed adenoid cystic carcinoma of the left external auditory canal, and we performed lateral temporal bone resection under general anesthesia. No local recurrence was observed 12 months postoperatively. Adenoid cystic carcinoma of the external auditory canal is rare; therefore, diagnosis is often delayed, and currently there is no established therapy, including surgical treatment. We report two rare cases of this malignancy, together with a review of the literature.