 Primary KRAS mutations generally lead to a self-limiting hyperplastic or borderline lesion, but if they occur after a previous APC mutation it often progresses to cancer.KRAS mutations are more commonly observed in cecal cancers than colorectal cancers located in any other places from ascending colon to rectum.KRAS mutation is predictive of a very poor response to panitumumab (Vectibix) and cetuximab (Erbitux) therapy in colorectal cancer.