Schwannoma of the sinonasal tract: a clinicopathologic and immunohistochemical study of 5 cases.

CONTEXT

Peripheral nerve sheath tumors are soft tissue neoplasms rarely encountered in the nasal cavity and paranasal sinuses.

OBJECTIVE

To describe the clinicopathologic and immunohistochemical features of a series of schwannomas of the sinonasal tract.

DESIGN

Surgical pathology files were searched for the diagnosis "sinonasal schwannoma." All histologic documents and clinical data were reviewed. Immunohistochemistry was performed on paraffin-embedded tissue with antibodies to S100 protein, epithelial membrane antigen, CD34, and MIB-1. RESULSTS: Five cases of sinonasal schwannoma were retrieved; patients included 3 women and 2 men, aged 20 to 56 years. Three cases were located in the ethmoid sinus. Clinical symptoms were nonspecific (nasal obstruction, epistaxis, and anosmia). All tumors were treated with conservative surgical resection. Pathologic examination showed a spindle cell proliferation without encapsulation in all cases. No cytologic atypia was seen, and the mitotic activity was low (<3 mitotic figures/10 high-power fields). Immunohistochemistry showed diffuse positivity with S100 protein and negativity with CD34 and epithelial membrane antigen. MIB-1 staining was low (1%-5% of tumor cell nuclei stained). During the follow-up (median, 6 years), no recurrence or metastasis was observed.

CONCLUSIONS

Schwannoma is a very unusual tumor of the sinonasal tract and is associated with nonspecific symptoms. Histologically, sinonasal schwannomas differ from schwannomas of other locations by their lack of a peripheral capsule and possible ulceration of the epithelial covering. Sinonasal schwannomas are treated with conservative surgical resection and have an excellent prognosis.