Work by multiple laboratories has demonstrated that the Nf1+/- microenvironment accelerates or, in some cases, is even required for the genesis of multiple benign NF1-associated tumors, including PNF [31,86,87], optic nerve glioma [88], and papilloma formation [87], in response to carcinogenic insult. The gene discussed is NF1; the disease is optic nerve glioma.