KRAS and colorectal carcinoma: The patient with a PR had a fresh biopsy taken within 7 days before treatment start and was found to have KRAS mutant MSS CRC and CRC consensus molecular subtype 4 (CMS4), the poor-prognosis mesenchymal subtype.8 Although this subtype is associated with TGF-β activation, this was not observed (Fig. 1C).