NF1 and malignant peripheral nerve sheath tumor: The cumulative lifetime risk of developing MPNST is 0.001% in the general population and 8%–13% in patients associated with NF-1.16,17) Notably, in the areas of existing internal PNs, the risk of developing MPNST is 20-fold higher.18) Patients with MPNST are usually symptomatic not due to compression but rather owing to the invasion of the corresponding structures and may present with respiratory and/or gastrointestinal symptoms.