MUC5AC and mucinous neoplasm: De novo expression of native MUC5AC in pancreatic tissues occurs in abnormal tissues ranging from benign diseases (pancreatitis) to precursor lesions (PanIN) to mucinous neoplasms and invasive adenocarcinomas; it is well-established in the literature and is attributed to considerable alterations at the gene expression level [15,31,32,33,34].