Malignant sinonasal epithelioid schwannoma.

Malignant schwannomas are rare neoplasms that are seldom found in the head and neck. Few cases have been reported involving paranasal sinuses and none of them was of the "epithelioid" type. In this report, an unusual case of epithelioid malignant schwannoma involving the maxillary sinus, nasal cavity and orbit is presented. The patient was a 27-year-old male with a history of headache, nasal obstruction and epistaxis. Histologically, the tumour had a biphasic pattern with spindle and epithelioid elements which led to a differential diagnosis with malignant melanoma. It had also to be distinguished from other neoplasms, such as squamous cell carcinoma and olfactory neuroblastoma because of it location. Immunohistochemical positivity for S-100 protein, glial fibrillary acidic protein and vimentin together with negativity for HMB-45 and cytokeratins, as well as mesaxon formation detected with electron microscopy were conclusive in the diagnosis. The patient was treated with surgical excision and radiotherapy but local recurrence and metastases occurred, and he died within 1 year after initial diagnosis.