Primary Pleomorphic Adenoma of the External Auditory Canal: A Case Report and Review of the Literature

Background. Pleomorphic adenoma (PA) is a benign tumour that mainly arises from salivary glands, and PA of the external auditory canal (EAC) is very rare. The objective of this study was to clarify the clinical presentation and treatment of PA of the EAC. Method. The authors present a case of PA arising from the EAC together with a literature review. Results. A 40-year-old man complained of hearing loss and foreign-body sensation of the right ear. Clinical and radiological examinations revealed a well-defined tumour limited to the EAC, with no connection to the parotid gland. Preoperative fine-needle aspiration cytology findings were characteristic of PA. The tumour was removed en bloc with the overlying skin. Conclusion. PA of the EAC is very rare, and methods to rule out malignancy before treatment are lacking. Thus, long-term follow-up is necessary, because malignant tumours are common in the EAC and PA has malignant potential. 1. Introduction Pleomorphic adenoma (PA) is a benign tumour that mainly arises from the salivary glands [1]. However, PA may also arise from the external auditory canal (EAC), although reports are very rare. Since 1951, when Mark and Rothberg published their first EAC pleomorphic adenoma report [2], at least 35 similar cases have been reported [3–13]. PA of the EAC is classified as a type of ceruminal gland tumour. The ceruminal glands may give rise to both benign and malignant tumours. According to the World Health Organization (WHO) classification [14], the benign tumours include adenoma, pleomorphic adenoma, and syringocystadenoma papilliferum, and the malignant tumours include adenocarcinoma, adenoid cystic carcinoma, and mucoepidermoid carcinoma. Ceruminal tumours are frequently malignant with a poor prognosis and extend to the middle ear inducing significant hearing loss [8]. PA arising from the EAC is the rarest type of ceruminal gland tumour, and there is a scarcity of information regarding differentiation between PA and malignant tumours. In this case report, we describe a rare finding of a PA arising from the EAC and review the literature on these tumours. 2. Case Report A 40-year-old man was admitted to our hospital with hearing loss and foreign-body sensation of the right ear that had been present for the previous 5-6 years. Ear discharge and pain were absent, but a tumour covered by normal skin was observed in the right EAC. A pure-tone audiogram revealed conductive hearing loss of 30？dB　(Figure 1). Figure 1: Preoperative pure-tone audiogram. A pure-tone audiogram revealed conductive hearing loss of 30？dB. A