S100A9 and cholangiocarcinoma: The methylation of p16 and p14 promoters in the bile of CCA patients is highly consistent with biliary malignancy compared with patients with benign biliary tract disease, implying that p16INK4a and p14ARF promoter methylation status is a candidate biomarker for the endoscopic diagnosis of biliary tract diseases, although the combined diagnosis of CCA is not sensitive.