The activity of RAS oncogene, which influences cell proliferation and tumor growth, was upregulated in 19 patients affected by extrahepatic cholangiocarcinoma, resulting in significantly higher mean serum levels of ACE (56.6 ± 27.4 U/l) as compared to patients with choledocolithiasis (32.9 ± 14.6 U/l) and controls (28.6 ± 10.6 U/l) [49]. Here, ACE is linked to neoplasm.