By using the Cre-loxP technology, Pedersen et al. showed that expression of oncogenic NRASG12D in melanocytes early during embryogenesis resulted in a mouse phenotype strongly resembling NCM in human beings (43) As NRAS mutations occur in benign lesions such as CMN, they are in itself insufficient for malignant transformation of melanocytes, and better insight in the genetic aberrations eventually leading to melanoma is needed. The gene discussed is NRAS; the disease is congenital mesoblastic nephroma.