Another gene associated with retinol metabolism but also a member in the CYP450 superfamily showed up in the prognostic model of ICC: CYP26A1. The protein it encodes is a cytochrome P450 monooxygenase involved in the metabolism of all-trans-retinoic acid (ATRA). Here, CYP20A1 is linked to intrahepatic cholangiocarcinoma.