Although initial trials have suggested no role for immunotherapy in CRC [23], Le et al. [24] showed that 40% of patients with CRC-mismatch repair deficiency (dMMR), treated with Pembrolizumab (MAb anti-PD-1) responded to therapy vs 0% of patients with CRC-mismatch repair proficiency (pMMR) . The gene discussed is PDCD1; the disease is colorectal carcinoma.