A Klatskin tumor (or hilar cholangiocarcinoma) is a cholangiocarcinoma (cancer of the biliary tree) occurring at the confluence of the right and left hepatic bile ducts. The disease was named after Gerald Klatskin, who in 1965 described 15 cases and found some characteristics for this type of cholangiocarcinoma

Cause
The cause of cholangiocarcinoma has not been defined. A number of pathologic conditions, however, resulting in either acute or chronic biliary tract epithelial injury may predispose to malignant change. Primary sclerosing cholangitis, an idiopathic inflammatory condition of the biliary tree, has been associated with the development of cholangiocarcinoma in up to 40% of patients. Congenital biliary cystic disease, such as choledochal cysts or Carolis disease, has also been associated with malignant transformation in up to 25% of cases. These conditions appear to be related to an anomalous pancreatico-biliary duct junction and, perhaps, are related to the reflux of pancreatic secretions into the bile duct. Chronic biliary tract parasitic infection, seen commonly in Southeast Asia due to Clonorchis sinensis and Opisthorchis viverrini, has also been identified as a risk factor. Although gallstones and cholecystectomy are not thought to be associated with an increased incidence of cholangiocarcinoma, hepatolithiasis and choledocholithiasis may predispose to malignant change. Further, industrial exposure to asbestos and nitrosamines, and the use of the radiologic contrast agent, Thorotrast (thorium dioxide), are considered to be risk factors for the development of cholangiocarcinoma.
Macimorelin (INN) – or Macrilen (trade name) – is a drug that was developed by Æterna Zentaris for use in the diagnosis of adult growth hormone deficiency. Macimorelin acetate, the salt formulation, is a synthetic growth hormone secretagogue receptor agonist. It is a growth hormone secretagogue receptor (ghrelin receptor) agonist causing release of growth hormone from the pituitary gland.Macimorelin acetate is described chemically as D-Tryptophanamide, 2-methylalanyl-N-[(1R)-1-(formylamino)-2-(1H-indol-3-yl)ethyl]-acetate. Macimorelin (Macrilen™) was invented and first synthesized by the research group of Professor Martinez at University of Montpellier, Centre National de la Recherche Scientitifique (CNRS), France. This transpired from a long-lasting research collaboration with Aeterna Zentaris. Aeterna Zentaris later in-licensed macimorelin as a development candidate from the CNRS and proceeded with the pre-clinical and clinical development of the compound. As of January 2014, it was in Phase III clinical trials. The phase III trial for growth hormone deficiency is expected to be complete in December 2016.As of December 2017, it became FDA-approved as a method to diagnose growth hormone deficiency. Traditionally, growth hormone deficiency was diagnosed via means of insulin tolerance test (IST) or glucagon stimulation test (GST). These two means are done parenterally, whereas Macrilen boasts an oral formulation for ease of administration for patients and providers. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication. See also
List of growth hormone secretagogues

References
External links
"Macimorelin". Drug Information Portal. U.S. National Library of Medicine. "Macimorelin acetate". Drug Information Portal. U.S. National Library of Medicine.