Schwannomas of the sinonasal tract and nasopharynx.

Approximately 45% of benign peripheral nerve sheath tumors occur in the head and neck region. Of these, schwannomas (neurilemomas) arising from the nasal cavity and paranasal sinuses account for less than 4%. Pathologic features of this subset are not well documented. We report a series of five cases of sinonasal schwannoma and one in the nasopharynx. The male-to-female ratio was equal, and the age at presentation ranged from 38 to 65 years of age (median, 52 yr). Four of the lesions were located within the nasal cavity, one arose from the maxillary sinus, and one originated in the nasopharynx, with extension into the Eustachian tube. Two cases showed local bony destruction, with intracranial extension. Presenting clinical symptoms included nasal obstruction, epistaxis, rhinorrhea, anosmia, facial swelling, headache, and serous otitis media; the two cases with intracranial spread also presented with visual disturbances. All of the six cases were treated by surgical excision. Clinical follow-up in five cases ranged from 6 to 48 months (median, 27 mo). Histologically, all of the lesions shared many cytomorphologic features common to schwannomas arising at other sites, and all of the six cases showed strong, diffuse immunoreactivity for S-100 protein. Four cases showed features of the cellular variant, and one showed focal granular cell change. An unusual and previously poorly documented histologic feature, distinct from schwannomas arising at most other anatomic sites, was a lack of encapsulation, which, when combined with hypercellularity, often raised suspicion of malignancy. Because none of the cases in this series has shown either local recurrence or postoperative metastasis to date, lack of encapsulation and locally destructive growth in an otherwise histologically typical schwannoma arising at this site should not suggest malignant potential.