Among KRAS, BRAF and NRAS mutations, only particular KRAS mutations showed evidence of preferential selection over mutations in other genes in pancreatic cancer and uterine carcinoma (Fig. 4a, b), whereas preferential selection across genes was predominantly in favour of BRAF and NRAS mutations in melanoma and thyroid cancer (Fig. 4c, d). This evidence concerns the gene NRAS and melanoma.