CDX2 and adenoma: Finally, similar to ampullary MCs,17 nonampullary SB‐MCs rarely have recognizable preinvasive components, suggesting that they might not follow the classical adenoma‐adenocarcinoma sequence, and they are frequently negative for CDX2 and CK20, which must be borne in mind in such cases so as not to misinterpret them as extraintestinal in origin.