To this end, we determined the mutation status of 50 patients with colorectal cancer from formalin-fixed paraffin embedded (FFPE) tissues and compared these results with those from the PCR–reverse sequence-specific oligonucleotide probe (PCR-rSSO) method, which is approved for in vitro diagnostic test for analyzing KRAS, NRAS and BRAF in patients with colorectal cancer in Japan [16]. Here, KRAS is linked to colorectal cancer.