Patients with dMMR metastatic colorectal cancer have been shown to have significant clinical responses to immunotherapy with antiprogrammed cell death 1 (PD-1)/antiprogrammed cell death ligand 1 (PD-L1) treatment in phase II trials21, in stark contrast to those in the MSS colorectal cancer subgroup where there was no objective response to immunotherapy.32 The gene discussed is CD274; the disease is colorectal cancer.