Discrepancies between the K-ras mutational status of primary colorectal cancers and corresponding liver metastases are found in codon 13

•K-ras mutation of the primary tumors and liver metastasis was investigated in the 43 colorectal cancer (CRC) patients.•K-ras mutation was evident in 17 cases (39.5%).•In 6 CRC from the 17 K-ras mutation cases, the mutation was evident only in liver metastasis, where it was found in codon 13.•The discrepancy of K-ras codon 13 between primary and metastatic lesions may explain clinical discrepancy of EGFR efficacy.

K-ras mutation status has remained elusive in the metastatic liver tumors of colorectal cancer (CRC) in contrast to the primary CRC tumors. In this study, K-ras mutational status of the primary and corresponding liver metastatic tumors was investigated in the 43 CRC patients. Codons 12 and 13 of K-ras were directly sequenced, and a K-ras mutation was evident in 17 cases (39.5%). In 6 cases, the K-ras mutation was evident only in the liver metastasis, but not in the primary CRC, where the mutation was found in codon 13. This discrepancy between primary and metastatic lesions with regard to codon 13 of the K-ras gene may explain the clinical discrepancy of EGFR antibody therapy. In conclusion, the current data may lead to the development of personalized medicine for recurrent CRC, although further validation study is still required.