We examined the expression of p-STAT3 and Ref-1 in mice that have conditional ablation Nf1 and Arf in neural crest-derived Schwann cells that spontaneously develop a full spectrum of NF1-associated nerve sheath tumours including plexiform and atypical neurofibroma as well as MPNST. The gene discussed is CDKN2A; the disease is plexiform neurofibroma.