The classical fusion is remaining all of the functional domains, sub-classical fusion maintaining the TK domain, but missing the Ig-like domains and non-classical fusion only containing the C-terminal tail of FGFR2. Classical fusions have been reported in a series of ICC cohorts, followed with frequent of FGFR2-BICC1 and rare of FGFR2-TACC3, FGFR2-MGEA5, FGFR2-KIAA1598, FGFR2-AFF3, and so on10,16–22. This evidence concerns the gene OGA and intrahepatic cholangiocarcinoma.