S100A6 and cholangiocarcinoma: Our study, including 112 patients with histologically confirmed CCA, demonstrates that despite a significantly up-regulated expression of S100A6 in human and murine CCA tumor samples, S100A6 serum levels are not suitable as a biomarker for the diagnosis of CCA, which is in contrast to previous findings, suggesting a role of serum S100A6 as a biomarker in other gastrointestinal malignancies.