PTCH1 and skin basal cell carcinoma: The most frequent genetic alterations occurring in BCC are mutations disturbing the hedgehog (SHH/PTCH1/SMO) pathway, predominantly loss-of-function mutations in PTCH1 but also activating mutations in SMO; these genes encode two transmembrane proteins, PTCH1 (also known as Patched1) and SMO (also known as Smoothened), respectively (14, 15).