6 Although numerous laboratories have focused on understanding the molecular evolution of MPNST from their benign counterparts, very few studies have attempted to characterize the intratumoral heterogeneity as it relates to MPNST metastasis.7,8 In an effort to define the genomic alterations important for tumor progression and explore intratumoral heterogeneity, we employed next generation sequencing technology to analyze MPNSTs from two patients with NF1 who each developed temporally and spatially distinct metastases over a period of 2–3 years. The gene discussed is NF1; the disease is neoplasm.