IDH1 and cholangiocarcinoma: The biomarkers specific for the clinical stage of CCA found in the PubMed were MUCI, HES1, and CFL1, among others, and the biomarkers related to metastasis were PTP4A3, FOXC2, CD151, FGFR2, and IDH1. R values obtained from the GEPIA database were derived from correlation values between four core genes and these eight genes.