In E‐CRC, two cases with MMR deficiency (including one case with MLH1 methylation) had a putative‐driver mutation of RNF43.The two identified mutations of RNF43 in E‐CRC were both p.Gly659fs (hotspot accounting for 41.7% of alteration30, 31). Here, RNF43 is linked to mismatch repair cancer syndrome 1.