PTEN and nevus: It has been reported that PTEN expression is uniformly high in nevus and markedly lower in melanoma samples.10, 35, 36 In melanomas, PTEN is functionally inactivated through genetic and epigenetic mechanisms, including promoter hypermethylation.25, 37 Loss of PTEN expression in murine nevi accelerates melanoma formation by allowing escape from oncogene‐induced senescence.38