The association between Hh signaling and tumourigenesis was initially established in patients diagnosed with Gorlin syndrome, or nevoid basal cell carcinoma syndrome (NBCCS), where almost all cases are characterized by PTCH1 loss of heterozygosity, leading to ligand-independent constitutive Hh pathway activation [64,65]. The gene discussed is PTCH1; the disease is nevoid basal cell carcinoma syndrome.