One prospective targeted sequencing study63 on 1134 CRC patients revealed that compared with distal colon cancer, MSS mCRC with the primary tumor located in the proximal colon is associated with worse survival rates, older age at diagnosis, increased mutations, and enrichment of oncogenic mutations in KRAS, BRAF, PIK3CA, AKT1, RNF43, and SMAD4, which also suggests differences in tumor metastasis mechanisms between proximal colon cancer and distal colon cancer. The gene discussed is SMAD4; the disease is neoplasm.