An encapsulated neoplasm in which the fundamental component is structurally identical to a syncytium of schwann cells. It is thought to arise from the neural crest. By convention the benign schwannoma is preferably known as neurilemmoma and the true or malignant schwannoma is designated simply as schwannoma. Although it is the most common malignancy of peripheral nerves, it is poorly understood. With neurofibromas, neurilemmomas make up at least 65% of all neurogenic tumours.