FGFR2 and cholangiocarcinoma: For example, high mutation rates of AR1D1A, FGFR2, PIK3CA, and TP53 proteins, high levels of microRNAs such as miR-21, and high levels of proteins and cytokines such as CK-19, MMP-7, osteopontin, periostin, and IL-6 have been found in CCA patient serum (Rompianesi, et al., 2021).