Plexiform Neurofibromas and Malignant Peripheral Nerve Sheath Tumors in Adults with Neurofibromatosis Type 1: Clinical Insights from a Large Cohort

Background Plexiform neurofibromas (PNs) and malignant peripheral nerve sheath tumors (MPNSTs) are major complications in adults with neurofibromatosis type 1; we analyzed their clinical features and management in a large cohort of 1,067 adults. Methods Clinical data from all adults seen at the Dutch NF1 expertise center (2004–2025) were retrospectively collected, including NF1 diagnostic features, genetic data and details on PNs and MPNSTs. Detailed information was recorded on up to three largest or most symptomatic PNs per patient. Five-year survival after MPNST and risk factors for MPNST were analyzed. Known genotype-phenotype associations were evaluated. Results Among 1,067 adult patients with NF1 (1,019 generalized, 48 mosaic), PNs were present in 47%. Surgical management was frequently limited by regrowth and complications. Overall, 5% of patients were deceased; the median age of death was 48 years, most commonly due to MPNST. MPNST occurred in 4% of the patients, predominantly in proximal body regions. The presence of nodular PNs was an independent risk factor for MPNST. Five-year survival after MPNST was 54.5%. 17q11.2 microdeletion was associated with a higher risk for MPNST. Conclusions This large cohort study highlights that PNs and the associated risk of malignant transformation represent a significant burden for individuals with NF1. The limitations of surgical management of PNs underscore the need for effective systemic therapies. The prognosis for MPNST remains poor. Regular follow-up is essential for all patients with NF1, particularly those in high-risk subgroups.