Interleukin-6 (IL-6), a growth factor for bile duct epithelium [229], has a sensitivity as high as 100% in diagnosing CCA [230], but a low specificity, considering its elevated levels in hepatocellular carcinoma, benign biliary disease, and metastatic lesions, limiting its specificity [231]. The gene discussed is IL6; the disease is cholangiocarcinoma.