[Retroperitoneal neurogenic sarcoma (malignant schwannoma) in a patient with multiple neurofibromatosis]

A case of fibromatosis with cutaneous and retroperitoneal localization is reported. The interest of the case is due to the transformation of one of the deep masses into malignant Schwannoma. The finding provides the basis for some critical remarks of clinical interest on von Recklinghausen's disease.