Temporal Bone Histopathology Case of the Month Schwannoma of the External Auditory Canal *Giuseppe Magliulo, *Mario Ciniglio Appiani, *Maria Giovanna Colicchio, *Gianna Pulice, and †Cira Rosaria Tiziana Di Gioia *‘‘Organi di Senso’’ Department, and ÞDepartment of Experimental Medicine, University ‘‘La Sapienza,’’ Rome, Italy Schwannomas are slow-growing, benign tumors of neurogenic origin. Although they can develop in almost all regions of the body, 5% to 45% of schwannomas are found in the head and neck region (1). Their localization in the external auditory canal (EAC) has rarely been reported. This article describes a case of schwannoma of the EAC. We analyze the differential diagnosis and clinical implications of this rare lesion. CASE REPORT A 20-year-old-man presented with a 2-year history of a slowly enlarging, indolent mass arising from the ante- roinferior wall of the left EAC associated with left sub- jective hearing loss. Examination revealed an ovoid mass arising from the anteroinferior wall of the left EAC. It had a smooth sur- face, was covered with normal skin, and nearly totally occluded the canal, hindering visualization of the under- lying tympanic membrane. Computed tomography con- firmed a soft tissue mass obliterating most of the EAC and arising from the anteroinferior wall of the ear canal. On magnetic resonance imaging with gadolinium, the lesion was limited to the left EAC but deeper in the parotid area. Surgery to remove the tumor through a retroauricular approach was planned. The tumor had partially eroded the anterior cartilage of the EAC, deeper in the parotid area. It was removed en bloc with the overlying skin following a cleavage plane between the tumor and parotid gland. The skin covering the anterior and inferior walls of the bony and cartilaginous EAC was reconstructed using a skin graft taken from the postauricular region. Histologic examination showed a well-circumscribed, encapsulated lesion containing highly cellular zones intermingled with less cellular areas (Fig. 1). The first region was characterized by stroma rich in fibrillar material and closely packed spindle cells with elongated and palisaded nuclei (Fig. 2) and eosinophilic cytoplasms. Bands of fusiform nuclei alternated with areas devoid of nuclei. The less cellular component was characterized by a looser structure with little cellularity. These findings were consistent with a diagnosis of schwannoma. At follow-up 3 years after surgery, the patient was tumor-free. DISCUSSION Schwannomas arising in the external auditory canal are extremely rare. Since the first report in 1960 by Carbonara and De Candia (2), only 12 cases have been reported worldwide. Clinically, they present as a slow enlarging mass with a smooth surface, covered with normal skin. They are usually hard and parenchymatous and are noninfiltrating. The symptoms are correlated exclusively with their enlargement. In the EAC, the clinical presentation may Address correspondence and reprint requests to Giuseppe Magliulo, M.D., University ‘‘La Sapienza,’’ Via Gregorio VII n. 80, 00165 Rome, Italy; E-mail: giuseppemagliuloorl@yahoo.com The authors declare no conflicts of interest. FIG. 1. Schwannoma. Highly cellular zones, Antoni A areas (arrows), intermingled with less cellular zones, Antoni B areas (triangles) (hematoxylin and eosin; original magnification, Â2.5). Otology & Neurotology 33:e13Ye14 Ó 2012, Otology & Neurotology, Inc. e13 Copyright © 2012 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.