Klatskin tumors are cholangiocarcinomas that develop at the point where the left and right hepatic ducts join to form the common hepatic duct. They are malignant tumors that were first described in 1965.
Cholangiocarcinomas (CCCs) are malignant tumors of the biliary tree that arise from the bile ducts or the liver. Klatskin tumors (KTs) are also referred to as hilar or perihilar cholangiocarcinomas . A large proportion of all cholangiocarcinomas are Klatskin tumors. They are usually undifferentiated and grow rapidly. The majority of occurrences of KTs are sporadic, however, the prevalence is still unknown.
Klatskin tumors are more common in men and are typically reported in older individuals in their 6th decade of life . KTs normally do not produce symptoms until they have progressed to a late stage. This contributes to their poor prognosis. When tumors grow large enough, they may cause obstructive jaundice . KTs are the most commonly reported cause of proximal biliary obstruction, accounting for approximately 80% of such cases . Other signs of disease are non-specific and include abdominal pain, loss of weight, malaise, and fatigue. Cholangitis is less frequently encountered.
KTs are known to metastasize to regional lymph nodes in the abdomen. Metastases can also occur to the head of the pancreas and can spread distally via the systemic or portal circulation.
Certain factors predispose individuals to the development of KTs, the most prominent being primary sclerosing cholangitis (PSC). It is thought to be responsible for up to 40% of KTs. Other risk factors include chronic inflammation of the biliary tree, parasitic infections, namely ascariasis and schistosomiasis, chemical substances exemplified by thorotrast (X-ray contrast) and asbestos, some congenital diseases of the biliary tree, liver cirrhosis, and cholelithiasis . Many patients have comorbidities such as inflammatory bowel disease and viral hepatitis  .
There are various clinical, laboratory and imaging studies that are needed in order to make the diagnosis of Klatskin tumor. Imaging techniques include:
Positron emission (PET): PET scans can be utilized to detect small tumors, as well as distant metastases .
Staging of the tumor is necessary for planning treatment, as advanced stages of KT are inoperable. Using the Bismuth-Corlette classification, there are four types of hilar CCCs, of which type IV is the most advanced, involving both hepatic ducts.
The resultant cholestasis from KTs can be detected by measuring the levels of tumor markers such as carbohydrate antigen 19-9 (CA 19-9) and carcinoembryonic antigen (CEA) . Levels of over 100 units per milliliter are a good diagnostic indicator for CCC in patients with PSC . Additionally, liver function tests (LFTs) may show elevated levels of parameters such as alkaline phosphate (ALP) and gamma-glutamyl transpeptidase (GGT).