KRAS mutation has been unambiguously identified as a marker of resistance to 
cetuximab-based treatment in metastatic colorectal cancer (mCRC) patients. 
However, most studies of KRAS mutation analysis have been performed using 
homogenously archived CRC specimens, and studies that compare freshly frozen 
specimens and formalin-fixed paraffin-embedded (FFPE) specimens of CRC are 
lacking. The aim of the present study was to evaluate the impact of tissue 
preservation on the determination of KRAS mutational status. A series of 131 
mCRC fresh-frozen tissues were first analyzed using both high-resolution melting 
(HRM) and direct sequencing. KRAS mutations were found in 47/131 (35.8%) using 
both approaches. Out of the 47 samples that were positive for KRAS mutations, 33 
had available matched FFPE specimens. Using HRM, 2/33 (6%) demonstrated 
suboptimal template amplification, and 2/33 (6%) expressed an erroneous 
wild-type KRAS profile. Using direct sequencing, 6/33 (18.1%) displayed a 
wild-type KRAS status, and 3/33 (9.1%) showed discordant mutations. Finally, the 
detection of KRAS mutations was lower among the FFPE samples compared with the 
freshly frozen samples, demonstrating that tissue processing clearly impacts the 
accuracy of KRAS genotyping.