SMAD4 and cancer: It confirmed the high frequency of SMAD4 mutations in cancers such as PAAD, COAD and READ but also revealed a relatively high frequency of the mutations in STAD, LUAD and ESCA and lower frequencies in many other cancers (e.g. CESC, LUSC, HNC and CHOL) that are much less studied in the context of SMAD4 deficiency.