Precancerous conditions of the biliary tract

Precancerous conditions of the biliary tract are changes to cells of the gallbladder or bile duct that make them more likely to develop into cancer. These conditions are not yet cancer. But if they aren’t treated, there is a chance that these changes will become biliary tract cancer.

Precancerous conditions of the biliary tract may be low or high grade, depending on how the cells look under a microscope. If they look like normal cells, they are low grade and there is only a small chance they will become cancer. If the cells don’t look at all like normal cells, they are high grade and there is a greater chance they will become cancer.

The precancerous conditions of the biliary tract that may develop into biliary tract cancer include:

• biliary intraepithelial neoplasia
• intraductal papillary neoplasm of the bile duct

• gallbladder polyps

Gallbladder polyps are the most common precancerous tumour of the biliary tract. They are abnormal growths in the innermost layer of the gallbladder (the mucosa).

Only about 5% of all gallbladder polyps are precancerous. Larger polyps (about 10 mm or larger) are more likely to be or become cancer. Doctors monitor polyps for any change in their size, which may be a sign the polyps are malignant. Polyps that are 10 mm or larger or that grow 2 mm or more may be surgically removed as a precaution. Most polyps cause no symptoms and are only found during imaging tests of the gallbladder that are done for another reason.

Gallbladder polyps are divided into 2 groups:

• non-neoplastic, also called a pseudotumour (such as cholesterol polyps)

• neoplastic (such as adenomas)

Only neoplastic polyps can become cancer. Most gallbladder polyps will never become cancerous.

Biliary intraepithelial neoplasia (BilIN) is one of the most common precancerous conditions of the biliary tract. It is caused by chronic inflammation and results in abnormal differentiation and growth of the epithelial cells in the inner lining of the gallbladder or bile duct. BilIN is divided into low grade and high grade by how different the cells look from normal epithelial cells. Low-grade biliary intraepithelial neoplasia can become high grade if the epithelial cells become less differentiated over time. High-grade biliary intraepithelial neoplasia is more likely to become cancer.

Intraductal papillary neoplasm of the bile duct (IPNB) is the second most common precancerous condition of the biliary tract. It causes abnormal differentiation and papillary or finger-like growths into the lumen (space within the bile duct) from the inner lining (epithelium) of the bile ducts. IPNB is divided into low grade and high grade by how different the cells look from normal epithelial cells. Low-grade IPNB can become high grade if the epithelial cells become less differentiated over time. High-grade IPNB is more likely to become cancer.