The stage of a cancer is how much there is and how far it has spread in your body. Your doctor uses exams and tests to find out the size of the cancer and where it is. Imaging tests can also show if the cancer has grown into nearby areas and if it has spread to other parts of your body. The stage of a cancer is one of the most important things to know when deciding how to treat the cancer.

The most commonly used system to stage bile duct cancer is the TNM system from the American Joint Committee on Cancer (AJCC).

The first step in staging is to find the value for each part of the TNM system. Here's what the letters stand for in the TNM system:

• T tells how far the main tumor has spread into the lining of the bile ducts and nearby tissue.
• N tells if the lymph nodes near the tumor have cancer in them.
• M tells if the cancer has spread ( metastasized) to distant organs in the body, such as the bone, lung, or lining of your belly (abdomen).

Numbers or letters after T, N, and M provide more details about each of these factors. There are also two other values that can be assigned:

• X means the doctor does not have enough information to assess the extent of the main tumor (TX), or if the lymph nodes have cancer cells in them (NX).
• 0 means no sign of cancer, such as no sign of the primary (main) tumor (T0).

The T, N, and M categories are put together to find the stage grouping. These groups give an overall description of the cancer. A stage grouping can have a value of 0 to 4, and they're written as Roman numerals 0, I, II, II, and IV. The higher the number, the more advanced the cancer is. Letters and numbers can be used after the Roman numeral to give more details.

Staging for bile duct cancer is complex, and it differs based on where the tumor is. The stage grouping used depends on which of these places the cancer first started:

• Within the liver: intrahepatic bile duct cancer
• Just outside the liver in the place called the hilum: perihilar (hilar) bile duct cancer
• Farther down in the bile duct system: distal bile duct cancer

These are the three stage groupings of bile duct cancer and what they mean:

Stage 0. The cancer is only in cells on the surface of the innermost layer of the bile duct, which is called the mucosa. This stage is also called carcinoma in situ (CIS).

Stage I. The cancer has not spread to nearby lymph nodes or to other parts of the body. This stage is divided into these two subgroups:

• Stage IA. The tumor is no more than 5 cm (centimeters) across. It has not grown into nearby blood vessels.
• Stage IB. The tumor is more than 5 cm across. It has not grown into nearby blood vessels.

Stage II. There's one tumor and it has grown into nearby blood vessels, or there's two or more tumors that may or may not have grown into nearby blood vessels. The cancer has not spread to nearby lymph nodes or to other parts of the body.

Stage III. The cancer has not spread to other parts of the body. This stage is divided into these two subgroups:

• Stage IIIA. The cancer has grown into the outer cover of organs in the belly (abdomen). This covering is called the visceral peritoneum. It has not spread to nearby lymph nodes.
• Stage IIIB. One of these is true:
  • The cancer has grown right into tissues or structures outside the liver. It has not spread to nearby lymph nodes.
  • The tumor is any size and may or may not be growing outside the bile duct. But it has spread to nearby lymph nodes.

Stage IV. The tumor is any size and may or may not be growing outside the bile duct. It may or may not have spread to nearby lymph nodes. The cancer has spread to organs in other parts of the body, such as the bone or lung.

Stage 0. The cancer is only in cells on the surface of the innermost layer of the bile duct, which is called the mucosa. This stage is also called carcinoma in situ (CIS).

Stage I. The cancer has grown deeper into the layers of tissue that make up the bile duct wall. It has not spread to nearby lymph nodes or to other parts of the body.

Stage II. The cancer has grown through the bile duct wall and into nearby fatty tissue or nearby liver tissue. It has not spread to nearby lymph nodes or to other parts of the body.

Stage III. The cancer has not spread to other parts of the body. This stage is divided into these three subgroups:

• Stage IIIA. The cancer is growing into one side of the main branches of a blood vessel in the liver, either the portal vein or the hepatic artery. It has not spread to nearby lymph nodes.
• Stage IIIB. The cancer has not spread to nearby lymph nodes. It's growing into the main blood vessels in the liver in one of these ways:
  • It's growing into the portal vein or the hepatic artery, the main blood vessels in the liver.
  • It's growing into the branches of the main portal vein on both side (left and right)
  • It's growing into other bile ducts on either the left or right sides and into a major blood vessel (the portal vein or the hepatic artery) on the other side.
• Stage IIIC. The tumor is any size. It may or may not be growing outside the bile duct or into nearby blood vessels. The cancer has spread to one to three nearby lymph nodes.

Stage IV. This stage is divided into these two subgroups:

• Stage IVA. The tumor is any size and may or may not be growing outside the bile duct or into nearby blood vessels. The cancer has spread to at least four nearby lymph nodes but not to other parts of the body.
• Stage IVB. The tumor is any size and may or may not be growing outside the bile duct or into nearby blood vessels. It may or may not have spread to nearby lymph nodes. It has spread to other parts of the body, like the lungs, bones, or to distant parts of the liver.

Stage 0. The cancer is only in cells on the surface of the innermost layer of the bile duct, which is called the mucosa. This stage is also called carcinoma in situ (CIS).

Stage I. The cancer has grown less than 5 mm (millimeters) deep into the bile duct wall. It has not spread to nearby lymph nodes or to other parts of the body.

Stage II. The cancer has not spread to other parts of the body. This stage is divided into these two subgroups:

• Stage IIA. One of these is true:
  • The cancer has grown 5 mm to 12 mm deep into the bile duct wall. It has not spread to nearby lymph nodes.
  • The cancer has grown less than 5 mm deep into the bile duct wall. It has spread to one to three nearby lymph nodes.
• Stage IIB. One of these is true:
  • The cancer has grown more than 12 mm deep into the bile duct wall. It has not spread to nearby lymph nodes.
  • The cancer has grown 5 mm or more deep into the bile duct wall. It has spread to one to three nearby lymph nodes.

Stage III. The cancer has not spread to other parts of the body. This stage is divided into these two subgroups:

• Stage IIIA. The cancer has grown into any depth of the bile duct wall. It has spread to four or more nearby lymph nodes.
• Stage IIIB. The cancer is growing into nearby blood vessels. It may or may not have spread to nearby lymph nodes.

Stage IV. The cancer has grown into any depth of the bile duct wall. It may or may not have spread to nearby blood vessels. It may or may not have spread to nearby lymph nodes. It has spread to other parts of the body, such as the liver, lung, or the lining of the abdomen (called the peritoneum).

Once your cancer is staged, your doctor will talk with you about what the stage means for your treatment.

Sometimes doctors use a simpler way to describe bile duct cancers. This is based on whether the cancer can be removed with surgery:

• Resectable cancers can be completely removed. Most stage 0, I, II, and some stage III cancers tend to be resectable.
• Unresectable cancers cannot be totally removed. They may have spread too far, or they are in a place that makes it hard to take out all of the tumor. Most stage III and all stage IV cancers are unresectable.

Make sure your doctor explains the stage of your cancer to you in a way you can understand. Ask any questions or talk about your concerns.