NF1 and papilloma: In a two-step 7,12-dimethylbenz[a]anthracene/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA) skin carcinogenesis model, the Nf1+/- microenvironment exhibited dueling roles by accelerating benign papilloma formation, while antagonizing malignant transformation to squamous cell carcinoma [87].