A cholangiocarcinoma occurring at the junction where the left and right hepatic ducts meet to form the common hepatic duct may be referred to eponymously as a Klatskin tumor.Although cholangiocarcinoma is known to have the histological and molecular features of an adenocarcinoma of epithelial cells lining the biliary tract, the actual cell of origin is unknown. Recent evidence has suggested that the initial transformed cell that generates the primary tumor may arise from a pluripotent hepatic stem cell. Cholangiocarcinoma is thought to develop through a series of stages – from early hyperplasia and metaplasia, through dysplasia, to the development of frank carcinoma – in a process similar to that seen in the development of colon cancer. Chronic inflammation and obstruction of the bile ducts, and the resulting impaired bile flow, are thought to play a role in this progression.Histologically, cholangiocarcinomas may vary from undifferentiated to well-differentiated. They are often surrounded by a brisk fibrotic or desmoplastic tissue response; in the presence of extensive fibrosis, it can be difficult to distinguish well-differentiated cholangiocarcinoma from normal reactive epithelium. There is no entirely specific immunohistochemical stain that can distinguish malignant from benign biliary ductal tissue, although staining for cytokeratins, carcinoembryonic antigen, and mucins may aid in diagnosis. Most tumors (>90%) are adenocarcinomas. Diagnosis
Blood tests
There are no specific blood tests that can diagnose cholangiocarcinoma by themselves. Serum levels of carcinoembryonic antigen (CEA) and CA19-9 are often elevated, but are not sensitive or specific enough to be used as a general screening tool.
Reinforce the tubercle by applying flowable composite. Occlusion, restoration, pulp and periapex assessment should be done yearly. When there is adequate pulp recession, tubercle can be removed and tooth can be restored.For teeth with normal pulp and immature apex, reduce the opposing occluding tooth. Apply flowable composite to the tubercle. Occlusion, restoration, pulp and periapex assessment should be done every 3–4 months until the apex matures. When there are signs of adequate pulp recession, tubercle can be removed and tooth can be restored.For teeth with inflamed pulp and mature apex, conventional root canal treatment could be carried out and restored accordingly.For teeth with inflamed pulp and immature apex, shallow MTA pulpotomy could be performed and then restore with glass ionomer and composite.For teeth with necrotic pulp and mature apex, conventional root canal therapy could be done and restored.For teeth with necrotic pulp and immature apex, MTA root-end barrier could be carried out. Glass ionomer layer and composite could be used to restore the tooth.If there is occlusal interference, the opposing projection should be reduced. Make sure that the tubercle does not contact other teeth in all excursive movement. This is usually done over a few appointments, 6 to 8 weeks apart to allow the formation of reparative dentin to protect the pulp. Fluoride varnish should be applied onto the ground surface. Recall the patient for follow-up after 3, 6 and 12 months.In some cases, extraction could be considered (e.g. for orthodontic purposes, failed apexification)

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