HNF1A and flatulence: Immunohistochemically, GAS is generally characterized as follows: negative ER, PR, vimentin, p16, p63, p40, AR, PAX2; positive Trefoil Factor 2 (TFF2), CK7, CEA, and CAIX; positive PAX8, MUC6, HIK1083 (60–80%); positive CK20 and CDX2 (50%); and positive HNF1 (90%).[4] The patient we tested showed P16 (−), PAX8 (+), PAX2 (−), ER (−), MUC6 (+), CK7 (+), CK20 (+, lesion), cdx-2 (+), and Vimentin (−), which are basically identical with the results reported in the relevant documents.