Malignant Schwannoma, recently renamed malignant peripheral nerve sheat tumor retroperitoneally localized, represents 0.01 of retroperitoneal tumours. A 41-year old woman, without pathological record--and without cutaneous neurofibromatosis--hospitalized for increased volume of the abdomen, without symptomatology, is diagnosed after the imaging and biological tests--without CT and RMN--with retroperitoneal tumour. The unusual size of tumour--6000 gr.--the macroscopic aspect suggesting malignancy (histopathologically and immunohistochemically confirmed), the relatively easy extirpation which, nevertheless, required caudal spleen- and pancreatectomy as well as transvers colectomy, the absence of proximity adenopathy and remote secondary determinations, the simple postoperative evolution represent overwhelming elements in this case. Two years after the operation, during which the patient was under chemotherapy, on a routine control we found a relapse at a distance from the initial tumour (primitive tumour ?), totally operable. For the time being, after almost five years from the first operation, there are no clinical, biological and imaging changes.
Conclusions: the retroperitoneal space is quite enough for the development of large tumour masses, without symptomatology. The present case combines most characteristics of retroperitoneal neoplasms: large or very large size, quasi-absent symptomatology, difficulty in preoperative diagnosis, surgical tactics and techniques--quite often, the total extirpation of tumour mass led to the sacrifice of other organs within the limits of a justified risk--and unforeseeable evolution with relapses having the same characteristics.