MUC5AC and pancreatic adenocarcinoma: Such an expression pattern, particularly the MUC1+/MUC2-/MUC5AC+ immunophenotype, is characteristic of pancreatic adenocarcinoma (Figs. 5 and 6).22 Although these findings furthered the supposition that this tissue is pancreatic in origin, it should be noted that this immunophenotype may also be present in cholangiocarcinoma.22 Although within the periampullary region, cancers of biliary origin are rarer than that of pancreatic origin, a cancer of biliary origin cannot be completely ruled out.23