KRAS and melanoma: Transgenic mouse models have established that oncogenic Kras can induce naevi and be a founder event in melanomagenesis.12 In one study, a KrasG12D allele was combined with alleles of p53 or Lkb1 and with a melanocyte-specific Cre driver to generate a model that developed melanoma with a penetrance of 100%.13 In this study, metastases were identified in lymph node, lung, liver and spleen but not in kidney or brain.