Considering the known dependence of severity and propensity of disease symptoms on genetic background in humans, we developed a murine model that closely resembles NBCCS by transferring Ptch1 heterozygosity from a tumor-resistant mouse strain (C57BL/6) to SKH-1, a strain that is highly susceptible to skin tumorigenesis [26]. This evidence concerns the gene PTCH1 and nevoid basal cell carcinoma syndrome.