PTCH1 and basal cell carcinoma: Figure 3 is a germline sample derived from peripheral blood containing a focal heterozygous deletion of exon 15 of the tumour suppressor gene PTCH1. Germline alterations in PTCH1 underlie the nevoid basal cell carcinoma syndrome or Gorlin syndrome, which is an autosomal dominant disorder predisposing to basal cell carcinomas.