KRAS and colorectal carcinoma: KRAS is mutated in over 40% of all CRC cases and in CRCs that have no mutations in KRAS, mutations in BRAF may occur (Bos et al, 1987; Forrester et al, 1987; Samowitz et al, 2005; Normanno et al, 2009; Ogino et al, 2009).