RESUMO
The occurrence of an isolated malignant peripheral nerve sheath tumor (MPNST) of the kidney capsule is extremely rare and its presence may only be expressed by an insidious onset of non-specific and misleading symptoms with a predominance of lower back pain. A computer tomography (CT) scan (as the imaging procedure of choice) will demonstrate the tumor location and its relation to the surrounding structures. Tumor excision in toto is considered the treatment of choice, but it can be hazardous, especially if the tumor is adhering to the surrounding structures. Severe bleeding complications due to the damage of venous structures have to be considered, and establishing hemostasis may pose considerable difficulties. Therefore surgery should be attempted with full precautions and the patient must receive preoperative counseling. If malignancy can safely be excluded, a laparoscopic excision should be considered as an alternative treatment as recurrence is unlikely. Definition of the originating nerve might not always be possible, and a minor degree of neurological impairment has therefore to be anticipated. A case of an isolated MPNST of the kidney capsule without neurofibromatosis is presented. The tumor was located in the fatty and fibrous capsule. It was surgically removed. The patient was further managed with radiotherapy and chemotherapy. An MPNST in such a location is very unusual.