KRAS and colorectal carcinoma: Briefly, four CMSs of CRC are recognized: CMS1 is characterized by MSI, mutations in the BRAF oncogene, a diffuse immune infiltrate, composed of Th1 cells and CTLs and a strong activation of immune evasion pathways; CMS2 tumors showed high chromosomal instability and activation of Wnt and MYC pathways; CMS3 displayed frequent KRAS mutations and disrupted metabolic pathways and CMS4 is characterized by high expression of mesenchymal genes, stromal infiltration, angiogenesis and transforming growth factor beta (TGF-β) activation (Figure 2).