A Case of Schwannoma of the External Auditory Canal

Abstract

In this report, we describe a clinical case of a schwannoma arising in the external auditory canal. A 45-year-old woman with a pituitary adenoma who was being followed up presented to our department with a mass in the external auditory canal detected using computed tomography (CT). Physical examination revealed a dull red and soft mass arising from the inferior and anterior wall of the right external auditory canal. There was no tenderness. CT images of the temporal bone demonstrated a well-circumscribed, soft tissue mass narrowing most of the external auditory canal. There was no bone erosion and no middle ear or mastoid involvement. A biopsy was performed before surgery, and she was diagnosed as having a myxoma. The patient underwent excisional surgery through a transmeatal approach under general anesthesia.

Histopathologic examination revealed areas of compact spindle cells arranged in short bundles. The tumor cells were composed of Antoni-A and Antoni-B areas. Immunohistochemical staining demonstrated positive staining of tumor cells for S-100. The final diagnosis was a schwannoma of the external auditory canal. Nine months postoperatively, there were no signs of local recurrence in the external auditory canal. In this case, the tumor arose from the interior and anterior wall of the right external auditory canal and was derived from the auriculotemporal nerve. Based on a careful review of the literature, we found 18 cases of schwannomas originating in the external auditory canal. In these reports, four cases were derived from the auriculotemporal nerve and seven cases were derived from the auricular branch of the vagus nerve (Arnold nerve). The treatment of benign tumors in the external auditory canal is excision with safety margins. If the tumor is large or the base of the tumor is wide or deep, a post-aural approach is better.