What Is The Prognosis For Neurofibrosarcoma?

i had a mass removed from my left thigh on october 21,my pathology report said is was a large cell undifferentiated,pleomorphic malignant neoplasm..it says it may represent a malignant neural tumor,possibly neurofibromasarcoma,i have neurofibromatosis(von recklinghausen's disease)...i have an appointment at a cancer center monday...if it is neurofibromasarcoma,what are my chances of surviving?