The gallbladder lies just below the liver in the upper abdomen, and is not considered part of the liver. The gallbladder stores bile, a fluid made by the liver that helps digest fat. Also called cholangiocarcinoma, these cancers arise from the epithelial cells of the bile ducts which carry bile from liver towards small intestine. According to American cancer society, cholangiocarcinoma is relatively uncommon in USA.
Almost all gallbladder cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).
Gallbladder cancer is hard to diagnose in the early stages because there are no signs or symptoms. Gallbladder cancer may be found when the gallbladder is checked for gallstones or removed.
Several disease conditions of the liver or bile ducts have increased risk of developing cholangiocarcinoma including primary sclerosing cholangitis, bile duct stones, choledocal cysts, cirrhosis of liver and infection with hepatitis B or C virus. About 30 percent of cholangiocarcinomas are diagnosed in patients with primary sclerosing cholangitis in which inflammation of the bile ducts (cholangitis) leads to the formation of scar tissue (sclerosing). Choledochal cysts are congenital cystic dilatations of the bile ducts, where overall incidence of cholangiocarcinoma is about 28 percent if these cysts are untreated.