A 67-year-old man with neurofibromatosis type 1 presented with multiple nodular swelling all over the body and a swelling arising from posterior aspect of right thigh suggestive of neurofibroma arising from the sciatic nerve with malignant potential. The chief complaint of patient was severe excruciating pain into the whole left lower limb. The differential diagnosis of malignant peripheral nerve sheath tumor, neurofibrosarcoma was based on clinical, radiological, and histological evidence. The tumor apparently originated in sciatic nerve at the posterior aspect of the right thigh. The tumor mass was excised completely without neural damage to the sciatic nerve. Patient is relieved of pain and totally asymptomatic after 2 year follow up.