![]() ![]() Radiologic imaging by CT shows schwannomas to be well-circumscribed, homogenous masses that enhance with contrast. Leiomyomas are positive for SMA and negative for S-100 while desmoplastic melanomas are positive for S-100 but lack the Antoni-A and Antoni-B pattern. They are usually multicentric, which is an important clinical distinction from schwannomas, and may be accompanied by a special entity called von Recklinghausen’s disease. Neurofibromas are not encapsulated and they lack the Antoni-A and Antoni-B pattern. Schwannomas should be differentiated from other spindle cell tumors such as neurofibroma, leiomyoma, and desmoplastic melanoma. ![]() Immunohistochemical staining usually shows positive staining for S-100 protein and negative for desmin and smooth muscle actin (SMA). A positive S-100 protein is indicative of Schwann cell origin. Areas consisting of a thick concentration of cells are called Antoni type A (Verocay body), whereas those in which the cells are loose and irregularly arranged are called Antoni type B. On histologic examination, the tumor is characterized by streams of elongated spindle cells, with the elongated nuclei often arrayed in a palisade pattern. A definitive diagnosis should be based on the histological and immunohistochemical findings. Ī differential diagnosis should be made with respect to a number of other soft tissue neoplasms such as fibroma, chondroma, and leiomyoma. The erosion of the bony canal wall was reported in one case. Schwannomas are encapsulated and therefore they can be easily dissected from the surrounding tissues. Neurogenic symptoms such as pain or paresthesia are uncommon. In the external auditory canal the clinical presentation may appear as recurrent external otitis and a mild conductive hearing loss secondary to obstruction of the canal from the tumor mass. The clinical presentation of schwannoma is usually a slow growing and asymptomatic mass. The diagnosis was made by histology and no relapses were reported after surgery. An excisional biopsy was done by transmeatal approach or postauricular approach. In all the cases a CT scan was performed and it showed a well-circumscribed, soft tissue mass narrowing the external auditory canal. Only one case was discovered by chance during a stapedectomy for otosclerosis. The range of ages in these cases was 18 to 59 years and most patients presented with a mass in their external auditory canal with or without progressive hearing loss. Only a few cases were reported in the literature. In the present case the tumor was located mainly at the inferior canal wall, which was supplied by the auricular nerve. Cutaneous sensory nerves that are covered by Schwann cells, from which schwannoma may originate, supply the external auditory meatus and canal. Most of the extracranial schwannomas in the head and neck originate from cutaneous or muscular branches of the cervical or brachial plexus. Those arising from the external auditory canal are very rare. In the head and neck, they are commonly seen in association with large nerve trunks. Schwannomas of the head and neck are common, and are mostly seen arising from the internal acoustic meatus. The mass arose from the inferior canal wall at the cartilaginous portion of his external auditory canal with no bone erosion and no middle ear or mastoid involvement. A computed tomography (CT) scan of the temporal bone demonstrated a well-circumscribed, soft tissue mass narrowing most of the external auditory canal (Fig. Laboratory analyses on admission are shown in Table 1. A neurological examination did not show any lesions in the central or peripheral nervous systems. A physical examination revealed a pale and firm mass arising from the inferior wall of his right external auditory canal that totally filled the external auditory canal. On admission, his blood pressure was 11/6 mmHg, heart rate was 70 beats/minute, and body temperature was 36.5 ☌. He did not smoke tobacco or consume alcohol. A 22-year-old white man presented with slowly developing right-side hearing loss over 4 years without external otitis. ![]()
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