NF1 and malignant peripheral nerve sheath tumor: Daimaru et al. further broadened the definition to encompass the sporadic forms in patients without NF-1, which, he argued, are microscopically comparable malignant schwannomas with focal rhabdomyoblasts, and tumors consisting predominantly of rhabdomyoblastic differentiation with focal Schwann cell elements occurring within a nerve or in patients with NF-1 [17].