MUC5AC and neoplasm: Immunostaining was conducted for the tumor markers mucin-1 (MUC1), mucin-2 (MUC2), mucin-5AC (MUC5AC), mucin-6 (MUC6), cytokeratin-7 (CK7), cytokeratin-19 (CK19), cytokeratin-20 (CK20), and tumor protein p53 (p53).