The top genes that were found to be abnormally expressed in CCA, with a frequency ranging from 10% to >50 depending on the topographical location (intra or extrahepatic), the population studied, and the method include TP53, KRAS, CDKN2/p16INK4, FGFR2 gene fusions, ERBB2, IDH1, and ARID1A [12,15,21]. Here, CDKN2A is linked to cholangiocarcinoma.