Staging is the process of finding out how far a cancer has spread. The stage (extent) of bile duct cancer is one of the most important factors in selecting treatment options and estimating a patient's outlook for recovery and survival (prognosis).
 

A staging system is a standardized way for members of the cancer care team to summarize the extent of a cancer's spread. The stage of a cancer is determined by the results of the physical exam, testing (such as imaging and other tests), and by the results of surgery if it has been done.
 

The American Joint Committee on Cancer (AJCC) TNM system

The major system used to describe the stages of bile duct cancer is the American Joint Committee on Cancer (AJCC) TNM system. There are actually 3 different staging systems for bile duct cancers, depending on where they start.
 

Intrahepatic bile duct cancers (those starting within the liver) are staged separately from extrahepatic bile duct cancers. Also, extrahepatic bile duct cancers are split into 2 groups: perihilar tumors and distal tumors. The TNM system for all bile duct cancers contains 3 key pieces of information:

• T describes whether the main tumor has invaded through the wall of the bile duct and whether it has invaded other nearby organs or tissues.

• N describes whether the cancer spread to nearby (regional) lymph nodes (bean-sized collections of immune system cells located throughout the body).

• M indicates whether the cancer has metastasized (spread) to other organs of the body. (The most common sites of bile duct cancer spread are the liver, peritoneum [the lining of the abdominal cavity], and the lungs.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors:

• The numbers 0 through 4 indicate increasing severity.
• The letter X means "cannot be assessed" because the information is not available.

Intrahepatic bile duct cancer

T categories
 

TX: No description of the tumor's extent is possible because of incomplete information.

T0: There is no evidence of a primary tumor.

Tis: Cancer cells are only growing in the mucosa (the innermost layer of the bile duct) and have not invaded deeper layers of the bile duct. This stage is also known as intramucosal carcinoma and was previously called carcinoma in situ.

T1: A single tumor that has grown into deeper layers of the bile duct wall, but it is still only in the bile duct. The cancer has not grown into any blood vessels.

T2: Split into 2 groups

T2a: A single tumor that has grown through the wall of the bile duct and into a blood vessel.

T2b: 2 or more tumors, which may (or may not) have grown into blood vessels

T3: The cancer has grown into nearby structures such as the intestine, stomach, common bile duct, abdominal wall, diaphragm, or lymph nodes around the portal vein.

T4: The cancer is spreading through the liver by growing along the bile ducts.
 

N categories
 

NX: Regional (nearby) lymph nodes cannot be assessed.

N0: The cancer has not spread to nearby lymph nodes.

N1: The cancer has spread to nearby lymph nodes.
 

M categories
 

MX: Distant spread (metastasis) cannot be assessed.

M0: The cancer has not spread to tissues or organs far away from the bile duct.

M1: The cancer has spread to tissues or organs far away from the bile duct.
 

Stage grouping

Once a patient's T, N, and M categories have been determined, this information is combined in a process called stage grouping. The stage is expressed in Roman numerals from stage 0 (the least advanced stage) to stage IV (the most advanced stage). Some stages are subdivided with letters.
 

Stage 0 (Tis, N0, M0): The cancer is only growing in the innermost layer of the bile duct (Tis) and has not spread to lymph nodes (N0) or distant sites (M0).

Stage I (T1, N0, M0): The cancer is a single tumor that has grown into deeper layers of the bile duct wall (T1), but it has not grown into any blood vessels. It has not spread to lymph nodes or distant sites.
 

Stage II (T2, N0, M0): The cancer is either a single tumor that has grown into a blood vessel (T2a) or there are multiple tumors (T2b). The cancer has not grown into any nearby organs or structures. It has not spread to nearby lymph nodes (N0) or distant sites (M0).
 

Stage III (T3, N0, M0): The cancer has grown into nearby structures such as the duodenum (first part of the small intestine), colon, stomach, abdominal wall, diaphragm, or lymph nodes around the portal vein (T3). It has not (N0) spread to nearby lymph nodes or distant sites.
 

Stage IV

Stage IVA (T4, N0, M0) OR (Any T, N1, M0): Either the cancer is spreading through the liver by growing along the bile ducts, OR the cancer has spread to nearby lymph nodes. It has not spread to distant sites.

Stage IVB (Any T, any N, M1): The cancer has spread to distant sites (M1).
 

Extrahepatic bile duct cancer of the perihilar bile ducts

T categories for perihilar bile duct cancer
 

TX: No description of the tumor's extent is possible because of incomplete information.
 

T0: There is no evidence of a primary tumor.
 

Tis: Cancer cells are only growing in the mucosa (the innermost layer of the bile duct) and have not invaded deeper layers of the bile duct. This stage is also known as intramucosal carcinoma and was previously called carcinoma in situ.
 

T1: The cancer has grown into deeper layers of the bile duct wall, such as the muscle layer or the fibrous tissue layer.
 

T2: The tumor has grown through the wall of the bile duct and into nearby tissue.

T2a: The tumor has grown through the wall of the bile duct and into surrounding fat.

T2b: The tumor has grown through the wall of the bile duct and into nearby liver tissue.
 

T3: The cancer is growing into branches of the main blood vessels of the liver on one side (the main blood vessels of the liver are the portal vein and the hepatic artery).
 

T4: The cancer is growing into the main blood vessels of the liver (the portal vein and or the common hepatic artery) or branches of these vessels on 2 sides, OR the cancer is growing directly into other bile ducts while part of the tumor is growing into one of the main blood vessels.
 

N categories for perihilar bile duct cancer
 

NX: Regional (nearby) lymph nodes cannot be assessed.

N0: The cancer has not spread to nearby lymph nodes.

N1: The cancer has spread to nearby lymph nodes, such as those along the cystic duct, the common bile duct, the hepatic artery, and the portal vein.

N2: The cancer has spread to lymph nodes further away from the tumor, such as those around the major blood vessels of the abdomen (such as the aorta, the vena cava, the celiac artery, and the superior mesenteric artery).
 

M categories
 

MX: Distant spread (metastasis) cannot be assessed.

M0: The cancer has not spread to tissues or organs far away from the bile duct.

M1: The cancer has spread to tissues or organs far away from the bile duct.