FLT4 and cholangiocarcinoma: In particular, we focused on VEGFR-3, the specific receptor for VEGF-C and VEGF-D, because (1) it is already known that VEGF-C/VEGF-D/VEGFR-3 signaling pathway is crucial for the growth and maintenance of tumors, including cholangiocarcinoma [25, 26] and hepatocellular carcinoma [27]; (2) VEGFR-3 is involved in cell proliferation during chronic cholestatic liver injury [18]; (3) VEGFR-3 expression is altered in response to chronic cholestatic liver injury [18, 28]; and (4) structural and functional changes occur in VEGFR-3-expressing cells during chronic cholestatic liver injury [4, 19].