Colon cancers with dMMR have distinct clinical and pathological features, including tumor site, differentiation, treatment response and survival, etc. The Kirsten rat sarcoma viral oncogene (KRAS) mutation status in codon 12 or 13 of exon 2 has been reported in approximately in 40% of patients with metastatic CRC, and recognized as a predictive marker of resistance to EGFR-targeted antibodies in colorectal cancers. The gene discussed is KRAS; the disease is colonic neoplasm.