KRAS and cancer: Oncogene KRAS mutations are rather rare in BRAF mutant colorectal cancers, occurring in 10% of such cancers in TCGA and in about 5% in the DFCI cohort, compared with 37.8% and 31.6% in cancers with BRAF and PIK3CA wild type and 64.8% and 43.3% of cancers with BRAF wild type and PIK3CA mutations (Figure 2A,B).