MUC5AC and cholangiocarcinoma: Several cancer biomarkers have been developed for intrahepatic cholangiocarcinoma (iCCA) diagnosis, including biliary alkaline phosphatase, carbohydrate antigen 19-9 (CA19-9), cholangiocarcinoma-associated carbohydrate antigen (CCA-CA), carcinoembryonic antigen (CEA), cytokeratine 19 fragment 21-1 (CYFRA 21-1), human telomerase reverse transcriptase (hTERT), interleukin-6 (IL6), matrix metalloproteinase-7 (MMP7), and mucin 5AC (MUC5AC) [3].