Since these tumors are not removed or biopsied in children with NF1, we specifically chose this Nf1 genetically-engineered mouse low-grade glioma model system, because it recapitulates many of the features seen in the human condition and has been successfully employed to evaluate promising targeted therapies now in clinical trial for children with the tumors [3–6] (http://clinicaltrials.org; NCT01089101, NCT01158651 and NCT01734512). The gene discussed is NF1; the disease is central nervous system cancer.