But in some cholangiocarcinoma patients, AHCYL1 presented tumor-promoting capacity through fusing with fibroblast growth factor receptor 2 (FGFR2) to form a chimeric protein which shows constitutive tyrosine phosphorylation in the activation loop of the FGFR2 kinase domain and the hyperactivation of MAPK 51. The gene discussed is AHCYL1; the disease is cholangiocarcinoma.