MALIGNANT TRANSFORMATION OF A PERIPHERAL- NERVE SHEATH TUMOR OF THE PARANASAL SINUSES

Background: Distinguishing schwannoma from neurofibroma of the paranas al sinuses can be difficult. Patients: We present the rare case of mal ignant peripheral nerve sheath tumor of the frontoethmoid complex that occurred in a patient who had suffered from schwannoma at the same si te 7 years before. The tumor was examined clinically, histologically, and immunhistochemically. Results: Although complete surgical excision of the primary tumor should have been an apparently adequate manageme nt for benign schwannoma, the tumor recurred and even metastasized int o the brain. The tumor was resistant to aggressive surgical therapy co mbined with adjuvant irradiation and gamma knife therapy. The results of histological examinations identified schwannian features of the pri mary tumor and clearly outlined differentiation to solitary neurofibro ma. Conclusions: Considering that schwannomas can be predominantly ben ign with foci of malignant areas and that there are reported cases of malignant transformation of benign schwannomas, the present consensus in management of small and low-grade malignant schwannomas is complete surgical excision with negative margins. The therapy of choice for hi gh-grade malignant schwannomas is aggressive surgical resection, with wide tumor free margins, combined with adjuvant irradiation and chemot herapy.