Gallbladder cancer is a cancer that starts in the gallbladder. In order to understand this cancer, it helps to know about the normal structure and function of the gallbladder.
The gallbladder is a small, pear-shaped organ located under the right lobe of the liver. Both the liver and the gallbladder are behind the right lower ribs. The gallbladder is usually about 3 to 4 inches long and normally no wider than 1 inch.
The gallbladder concentrates and stores bile, a fluid made in the liver. Bile helps digest the fats in foods as they pass through the small intestine. Bile may be released from the liver directly into the small intestine, or it may be stored in the gallbladder and released later. When food (especially fatty food) is being digested, the gallbladder contracts and releases bile through a small tube called the cystic duct. The cystic duct joins up with the hepatic duct, which comes from the liver, to form the common bile duct. The common bile duct empties into the small intestine.
The gallbladder is helpful, but you do not need it to live. Many people live normal lives after having their gallbladders removed.
More than 9 out of 10 gallbladder cancers are adenocarcinomas. An adenocarcinoma is a cancer that starts in the cells with gland-like properties that line many internal and external surfaces of the body (including the inside the digestive system).
A type of gallbladder adenocarcinoma that deserves special mention is called papillary adenocarcinoma or just papillary cancer. These are gallbladder cancers whose cells are arranged in finger-like projections when viewed under a microscope. In general, papillary cancers are not as likely to grow into the liver or nearby lymph nodes. They tend to have a better prognosis (outlook) than most other kinds of gallbladder adenocarcinomas. About 6% of all gallbladder cancers are papillary adenocarcinomas.
There are other types of cancer that can develop in the gallbladder, such as adenosquamous carcinomas, squamous cell carcinomas, and small cell carcinomas, but these are uncommon.