Surveillance for Malignant Transformation of Neurofibromatosis Type 1 (NF1) Related Peripheral Nerve Sheath Tumors (PNST)

* INCLUSION CRITERIA: High-Risk and Low-Risk NF1 Cohorts * Age \>= 3 years old * Participants with clinical or genetic diagnosis of NF1. * Participants with a diagnosis of mosaic or segmental NF1 are also eligible. * Individuals may have (High-Risk Cohort) or not have (Low-Risk Cohort) at least one of the following characteristics: * Microdeletion or 844-848 missense variants or other variants associated with increased risk of malignant peripheral nervous sheath tumor (MPNST) * Family history of MPNST / atypical neurofibromatous neoplasm of unknown biologic potential (ANNUBP) / atypical neurofibromas (ANF) * Personal history of MPNST/ANNUBP/ANF or neurofibroma with CDKN2A/B loss * Prior radiation therapy at any site * Large plexiform neurofibroma (PN) burden (\>= 350 mL) * Presence \>= 1 DNL at baseline * The ability of the individual, parent/guardian or Legally Authorized Representative (LAR) to understand and the willingness to sign a written consent document for participation. EXCLUSION CRITERIA: High-Risk and Low-Risk NF1 Cohorts \- Inability or unwillingness to undergo MRI imaging INCLUSION CRITERIA: Parent Cohort * Parent or guardian of pediatric individuals (8-17 years old) in High-Risk or Low-Risk Cohorts. * The ability of the parent/guardian or LAR to understand and the willingness to sign a written consent document for parent/guardian participation in this study. EXCLUSION CRITERIA: Parent Cohort \- None.