Also, data emerging from mouse models are not conclusive since patch knockout mice develop more BCCs than wild mice when exposed to ultraviolet (UV) but about one-third of skin tumors develop in absence of exposure to external genotoxic stress [29] Ptch1-deficent mice develop several basaloid hyperproliferation but these cancer precursors progress to nodular and infiltrative BCCs only in X-ray irradiated areas [31]. The gene discussed is PTCH1; the disease is skin neoplasm.