Cholangiocarcinoma overview

# Overview
Cholangiocarcinoma refers to the malignant tumor of bile ducts. The epithelial cell lining the bile ducts are called cholangiocytes. The malignant transformsation of cholangiocytes leads to cholangiocarcinoma. Malignant transformation of cholangiocytes into cholangiocarcinoma include hyperplasia, metaplasia and dysplasia. Biliary intraepithelial neoplasia is believed to be the initial lesion of cholangiocarcinoma, particularly in patients with hepatolithiasis in bile ducts. On the basis of location, cholangiocarcinoma may be classified into extrahepatic cholangiocarcinoma, perihilar cholangiocarcinoma, and intrahepatic cholangiocarcinoma. Cholangiocarcinoma must be differentiated from other diseases that cause jaundice, abdominal pain, weight loss, and fatigue, such as gallbladder cancer, hepatocellular carcinoma, pancreatic cancer, cholecystitis, and choledochitis. Common complications of cholangiocarcinoma include infection, liver failure, and tumor metastasis. Prognosis is generally poor, and the survival rate of patients with cholangiocarcinoma mainly depends on extent of the tumor and resectability. The common symptoms of cholangiocarcinoma include jaundice, pruritis, abdominal pain, weight loss. Common physical examination findings of cholangiocarcinoma include jaundice, icteric sclera, hepatomegaly, right upper quadrant mass, and palpable gall bladder. The mainstay of treatment for cholangiocarcinoma is surgical resection. Surgical resection of tumors with negative margins is the best option for all subtypes of cholangiocarcinoma. Chemotherapy is indicated for unresectable cholangiocarcinoma as palliative chemotherapy. Chemotherapy agents used to treat cholangiocarcinoma include 5-fluorouracil, gemcitabine, irinotecan, cisplatin, or doxorubicin.

# Classification
Cholangiocarcinoma may be classified according to location of the tumor into three subtypes such as extrahepatic bile duct cancer, perihilar bile duct cancer, and intrahepatic bile duct cancer. Perihilar cholangiocarcinoma may be classified according to Bismuth-Corlette classification into five subtypes based on the extent of ductal infiltration.

# Pathophysiology
The epithelial cell lining the bile ducts are called cholangiocytes. The malignant transformsation of cholangiocytes leads to cholangiocarcinoma. Malignant transformation of cholangiocytes into cholangiocarcinoma include hyperplasia, metaplasia and dysplasia. Biliary intraepithelial neoplasia is believed to be the initial lesion of cholangiocarcinoma, particularly in patients with hepatolithiasis in bile ducts.

# Causes
There are no established causes for cholangiocarcinoma.

# Differential Diagnosis
Cholangiocarcinoma must be differentiated from other diseases that cause jaundice, abdominal pain, weight loss, and fatigue, such as gallbladder cancer, hepatocellular carcinoma, pancreatic cancer, cholecystitis, and choledochitis.

# Epidemiology and Demographics
The incidence of cholangiocarcinoma is approximately 1-2 per 100,000 individuals in the United States. The prevalence of cholangiocarcinoma is approximately 0.01% to 0.46% per 100,000 individuals. Patients of all age groups may develop cholangiocarcinoma. Cholangiocarcinoma is more common in males than in females.

# Risk Factors
Common risk factors in the development of cholangiocarcinoma are chronic inflammatory conditions of bile duct, liver fluke infections, choledochal cysts, toxins, and viral infections.

# Screening
According to the the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for cholangiocarcinoma.

# Natural history, Complications and Prognosis
Common complications of cholangiocarcinoma include infection, liver failure, and tumor metastasis. Prognosis is generally poor, and the survival rate of patients with cholangiocarcinoma mainly depends on extent of the tumor and resectability. Even with resection, prognosis is poor with 5-year survival of only 10-44%. The presence of primary sclerosing cholangitis is associated with a particularly poor prognosis among patients with cholangiocarcinoma.

# Diagnosis

## Staging
The staging of cholangiocarcinoma varies depending on whether the tumor is primarily intrahepatic (ICC), hilar/perihilar (Klatskin), or extrahepatic. Current staging classifications of intrahepatic cholangiocarcinoma include UICC system, Okabayashi system, and AJCC system. Current staging classifications of perihilar cholangiocarcinoma include MSKCC system and AJCC system.

## History and Symptoms
The common symptoms of cholangiocarcinoma include jaundice, pruritis, abdominal pain, weight loss.

## Physical Examination
Common physical examination findings of cholangiocarcinoma include jaundice, icteric sclera, hepatomegaly, right upper quadrant mass, and palpable gall bladder.

## Laboratory Findings
Laboratory tests for cholangiocarcinoma include aspartate aminotransferase (AST) and alanine aminotransferase (ALT), prothrombin time, albumin and total protein, bilirubin, L-Lactate dehydrogenase and alkaline phosphatase.

## CT
On CT scan, cholangiocarcinoma is characterized by homogenously low in attenuation and demonstrate heterogenous minor peripheral enhancement with gradual enhancement centrally. Capsular retraction may be observed. Bile ducts distal to the mass are typically dilated.

## MRI
On MRI, cholangiocarcinoma is characterized by either isointense or hypointense relative to the normal liver on T1 and mildly to markedly hyperintense on T2. Moderate to incomplete enhancement is observed on contrast MRI.

## Abdominal Ultrasound
On abdominal ultrasound, cholangiocarcinoma is characterized by obstruction and dilation of bile ducts. Mass-forming intrahepatic cholangiocarcinoma is characterized by homogeneous mass of intermediate echogenicity with a peripheral hypoechoic halo of compressed liver. Periductal infiltrating intrahepatic cholangiocarcinoma is characterized by capsular retraction. Intraductal cholangiocarcinoma is characterized by alterations in duct caliber, usually duct ectasia with or without a visible mass.

## Other Imaging Findings
Other imaging studies for cholangiocarcinoma include endoscopic retrograde cholangiopancreatography, endoscopic ultrasound, percutaneous transhepatic cholangiography, and MRCP.

## Other Diagnostic Studies
No additional tests are recommended for the diagnosis of cholangiocarcinoma.

# Treatment

## Medical Therapy
Chemotherapy is indicated for unresectable cholangiocarcinoma as palliative chemotherapy. Chemotherapy agents used to treat cholangiocarcinoma include 5-fluorouracil, gemcitabine, irinotecan, cisplatin, or doxorubicin.

## Surgery
The mainstay of treatment for cholangiocarcinoma is surgical resection. Surgical resection of tumors with negative margins is the best option for all subtypes of cholangiocarcinoma.

## Prevention
Effective measures for the primary prevention of cholangiocarcinoma hepatitis B vaccination, weight reduction, avoiding excess alcohol use.