Abstract Retroperitoneal pelvic neurofibrosarcoma is a rare tumor, and taking pathologic synonyms into account, only six cases could be found in the literature. The patient herein discussed presented with a cutaneous neurofibroma, and after its removal evidence of involvement of the pelvic nerve trunk appeared. The case confirms the impression that incomplete removal of these tumors encourages local recurrence with increased cellular anaplasia. Total resection is the treatment of choice, and the prognosis is probably better than for other retroperitoneal tumors. These tumors respond very poorly to radiotherapy.