Malignant epithelioid schwannoma of superficial soft tissue? A case report with immunohistology and electron microscopy.

Malignant epithelioid schwannoma is a well-defined entity. However epithelioid tumours arising other than in a nerve trunk, in a benign nerve sheath tumour or in neurofibromatosis are problematical. We describe a case of a nodular tumour of the cheek which recurred twice without metastasis. Light microscopy showed an amelanotic epithelioid tumour. Immunohistology showed positive staining for vimentin and S100 protein and electron microscopy showed distinctive appearances suggestive of schwannoma. We discuss the differential diagnosis of the tumour, compare it with reported tumours resembling both melanoma and schwannoma and conclude that this may be a further example of the distinctive tumour reported as "malignant epithelioid schwannoma of superficial soft tissues'.