Several studies have now shown that basic leucine zipper (bZIP) domain mutations in CEBPA confer a better prognosis with a distinct gene expression profile [29–31], so this is now an AML-defining genetic alteration in both classification systems, though the WHO still also includes other bi-allelic CEBPA mutations, while the ICC does not. The gene discussed is CEBPA; the disease is intrahepatic cholangiocarcinoma.