KRAS and colorectal cancer: In this study, we identify a novel double mutation outside of codons 12 and 13, recoding K-RAS codon 19 from leucine to phenylalanine (L19F) and codon 20 from threonine to alanine (T20A), in a colorectal cancer and we demonstrate that it causes transformation in vitro and is therefore a rare, but functionally significant co-mutation of K-RAS.