Metastatic CRC has been classified by histology, sidedness, genetic alterations such as those in wingless-type MMTV integration site family member (wnt)/β-catenin, transforming growth factor beta/mothers against decapentaplegic homolog 4 (TGFβ/SMAD4), rat sarcoma (RAS), tumor protein 53 (TP53), mismatch repair pathways, and consensus molecular subtypes based on RNA expression profiles [27]. The gene discussed is SMAD4; the disease is colorectal carcinoma.