Malignant schwannoma is a malignant neoplasm of nerve sheath origin. It develops in an unaltered nerve or in a neurofibroma, and rarely, if ever, within a neurilernmoma. We experienced a malignant schwannoma in a 75-year-old man without von Recklinghausen's syndrome. The lesion was solitary and polypoid, fungating nodule in the posterior portion of the left thigh, The tumor cells had some features of Schwann cells and positively stained to S-100 protein and neuron-specific enolase. Complete excision was performed but the associated nerve could not be demonstrable.