In addition, previous studies showing the association between NGF and CCA have been reported form Asian countries, and a study analyzing 93 CCA tumor tissues from Caucasian patients has reported that NGF-β and all Trk isoforms (A, B, and C) could not be detected from these Caucasian samples, regardless of the location of CCA (intrahepatic, hilar, or distal) [78]. Here, NGF is linked to cholangiocarcinoma.