Subsequently, different studies reported that approximately 30% of cutaneous melanoma cell lines harbor PTEN mutations or deletions (Guldberg et al., 1997; Tsao et al., 1998) and in vitro studies were performed attesting the involvement of PTEN LOH in the development of more than 30–40% of melanomas (Robertson et al., 1998). This evidence concerns the gene PTEN and cutaneous melanoma.