Type I HH pathway activation includes gain-of-function mutations in SHH that contribute to the formation of basal cell carcinoma, and heterozygous loss-of-function mutations in PTCH1 which cause Gorlin syndrome, basal cell cancers, and a range of other neoplasms including medulloblastoma [44,45,46]. This evidence concerns the gene PTCH1 and basal cell carcinoma.