SMO and neoplasm: These data are supported by preclinical models, with tumours histologically consistent with embryonal rhabdomyosarcoma developing in 10% of Ptch1± mice on the CD1 genetic background and also in mice with a SMO point mutation (SmoM2–W535L) leading to constitutive Hh pathway activation in non-myogenic endothelial progenitor cells, resulting in a block in myogenesis and driving tumorigenesis [101, 102].