Cancerous tumours of the biliary tract

A cancerous tumour of the biliary tract can grow into and destroy nearby tissue. It can also spread (metastasize) to other parts of the body. Cancerous tumours are also called malignant tumours.

There are several types of biliary tract cancer. They are grouped by their organ of origin, which cells the cancer started in, the tumour's patterns of growth and how the cells look under a microscope. When cancer starts in gallbladder cells, it is called primary gallbladder cancer. When cancer starts in bile duct cells, it is called primary bile duct cancer.

Gallbladder cancer is separated into 3 groups based on the appearance and behaviour of the tumour:

• An infiltrative tumour has an irregular shape and spreads quickly into the wall of the gallbladder. This is the most common form of gallbladder cancer.

• A nodular ( also called mass-forming) tumour looks like small, round lumps. It often grows through the wall of the gallbladder and spreads quickly into surrounding structures.

• A papillary tumour looks like a cauliflower. It grows into the gallbladder cavity and is less likely to spread, so it tends to have a better prognosis.

Bile duct cancer is separated into 3 groups based on the appearance and behaviour of the tumour:

• A nodular ( also called mass-forming or exophytic) tumour grows outward from the innermost layer of the bile duct.

• A periductal-infiltrating tumour grows along the bile ducts. It may also be called infiltrating or sclerosing bile duct cancer.

• An intraductal-growing tumour into grows into the lumen or space within the bile duct. It is sometimes called papillary or polypoid bile duct cancer.

Adenocarcinoma is the most common type of biliary tract cancer. It makes up about 90% of all cancers of the biliary tract. Adenocarcinoma starts in the epithelial cells lining the walls of the inside of the biliary tract.

Adenocarcinoma that starts in the gallbladder is called gallbladder adenocarcinoma. It is categorized based on how the cells look under a microscope. The subtypes of gallbladder adenocarcinoma include:

• non-papillary, or not otherwise specified, adenocarcinoma
• papillary adenocarcinoma
• mucinous adenocarcinoma

Non-papillary adenocarcinoma is the most common subtype of gallbladder cancer.

Adenocarcinoma that starts in the bile ducts is called cholangiocarcinoma (CCA). It is categorized based on the part of the bile duct where the cancer started. The subtypes of cholangiocarcinoma include:

• intrahepatic cholangiocarcinoma (iCCA)
• perihilar cholangiocarcinoma (pCCA)
• distal cholangiocarcinoma (dCCA)

Distal cholangiocarcinoma is the most common subtype of bile duct cancer.

Like other types of gallbladder and bile duct cancers, gallbladder adenocarcinoma and cholangiocarcinoma can also be grouped by how the tumours look and act in addition to categorizing them by how the cells look or by their location.

Rare cancers of the biliary tract include:

• squamous cell carcinoma

• adenosquamous carcinoma
• small cell carcinoma (also called oat cell carcinoma)
• signet ring cell carcinoma
• soft tissue sarcoma
• lymphoma
• neuroendocrine tumours (NET)

They are often more aggressive (grow and spread more quickly) and have a worse prognosis than adenocarcinoma.