KRAS and colorectal carcinoma: Traditionally CRC has been classified into three molecular subgroups based on the mechanism of carcinogenesis: chromosomal instability (APC (adenomatous polyposis coli) inactivation, Wnt (wingless-related integration site) signaling activation, activating KRAS (Kirsten rat sarcoma viral oncogene homolog) mutations), defects in DNA mismatch repair (Microsatellite Instability—MSI) and aberrant CpG island hypermethylation and gene silencing (CIMP, BRAF (v-RAF murine sarcoma viral oncogene homolog B1) mutations) [3,4].