CSF1R and cholangiocarcinoma: The tumor tissue-specific expression of the three identified plasma markers and their respective receptors (CSF1: CSF1-R; TRAIL: TRAIL-R1/TNFRSF10A, TRAIL-R2/TNFRSF10B, TRAIL-R3/TNFRSF10C and TRAIL-R4/TNFRSF10D) or ligands (TIE2/TEK: ANGPT1, ANGPT2 and ANGPT4) was then analyzed with gene expression data from two external surgical CCA cohorts with samples included from both tumor and normal surrounding liver: GSE107943 published by Ahn et al.