While neurofibromas can develop in both NF1+/+ and NF1+/- microenvironments (122), a recent study found that a heterotypic population of differentiating NF1-/- Schwann cells and NF1+/- pNF-derived fibroblasts provided the most potent cell mixture for generating pNFs in vitro and in vivo (154). The gene discussed is NF1; the disease is neurofibroma.