PTCH1 and skin basal cell carcinoma: Subsequently it was found that essentially all BCCs, sporadic or part of the BCNS, have mutations in PTCH1 or other elements of the HH signaling pathway (Aszterbaum et al., 1998), and nearly all BCC in humans or mice overexpress Ptch1 or one of the other components of the HH pathway (Tojo et al., 1999; Bonifas et al., 2001).