Database queries failed to uncover the same 21 nucleotide insertion in other tumour specimens; however, two lung adenocarcinomas and a colorectal cancer annotated in the COSMIC database contained a tandem duplication inserting five amino acids into K-Ras at the same location in the switch 2 domain (c.184_198dup; Fig. 1c). Here, KRAS is linked to lung adenocarcinoma.