Immunohistochemically, HNF4α expression was correlated with a loss of SMARCA4 (p = 0.035) and MUC5AC expression (p < 0.001), and inversely correlated with the expression of TTF-1 (p < 0.001) (Table 1), but seven samples were double-positive for TTF-1 and HNF4α, including six papillary adenocarcinomas and one solid adenocarcinoma. The gene discussed is MUC5AC; the disease is papillary adenocarcinoma.