How is gallbladder cancer staged?
Staging is the process of finding out how far a cancer has spread. The stage of gallbladder cancer is one of the most important factors in selecting treatment options and estimating a patient's prognosis (outlook for recovery).
A staging system is a standard way for members of the cancer care team to describe the extent of a cancer's spread. The stage of a cancer is determined from the results of the physical exam, imaging tests (ultrasound, CT or MRI scan, etc.) and other tests, which are described in the section, "How is gallbladder cancer diagnosed?" 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 gallbladder cancer is the American Joint Committee on Cancer (AJCC) TNM system. This system is also used to stage cancers that start in the cystic duct (the tube that carries bile away from the gallbladder). This system is based on 3 key pieces of information:
- T describes how far the primary tumor has grown into the wall of the gallbladder and whether it has grown into other nearby organs or tissues.
- N describes whether the cancer has 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 gallbladder cancer spread are the liver, peritoneum [the lining of the abdominal cavity], and the lungs.)
Numbers or letters after T, N, and M 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.
Nearly all gallbladder cancers begin in the tissue on the inside wall of the gallbladder. Over time they grow deeper into the gallbladder wall, pushing through the various layers toward the outside of the gallbladder.
The gallbladder wall has several layers. From the inside out, these are:
- The epithelium, a thin sheet of cells closest to the inside of the gallbladder
- The lamina propria, a thin layer of loose connective tissue (the epithelium plus the lamina propria form the mucosa)
- The muscularis, a layer of muscular tissue that helps the gallbladder contract, squirting its bile into the bile duct
- The perimuscular ("around the muscle") fibrous tissue, another layer of connective tissue
- The serosa, the outer covering of the gallbladder that comes from the peritoneum, which is the lining of the abdominal cavity
The tumor may grow to fill some or all of the space inside the gallbladder at the same time that it grows through the various layers of gallbladder in the opposite direction. If it grows through the gallbladder wall, the tumor may invade nearby organs, such as the liver, by growing directly into those organs, or it may enter the lymphatic or blood vessels within the gallbladder wall and spread to lymph nodes, the liver, and other parts of the body.
T groups for gallbladder cancer
TX: No description of the tumor's extent is possible because of incomplete information.
T0: No evidence of primary tumor.
Tis: Cancer cells are only found in the epithelium (the innermost layer of the gallbladder) and have not grown into (invaded) deeper layers of the gallbladder. This is also known as carcinoma in situ.
T1: The tumor has grown into the lamina propria or the muscle layer (muscularis).
- T1a: Tumor has grown into lamina propria.
- T1b: Tumor has grown into the muscularis.
T2: The tumor has grown into perimuscular fibrous tissue.
T3: The tumor has grown through the serosa (the outermost covering of the gallbladder) and/or it has grown from the gallbladder directly into the liver and/or one nearby structure such as the stomach, duodenum (first part of the small intestine), colon, pancreas, or bile ducts outside the liver.
T4: The tumor has grown into one of the main blood vessels leading into the liver (portal vein or hepatic artery) or it has grown into 2 or more organs outside of the liver.
Generally speaking, most doctors think T3 tumors are potentially resectable (removable by surgery), while T4 tumors are not. However, there may be other factors that affect whether surgery is a good treatment option in any given case.
N groups for gallbladder cancer
NX: Regional (nearby) lymph nodes cannot be assessed.
N0: The cancer has not spread to regional lymph nodes.
N1: The cancer has spread to lymph nodes near the gallbladder, such as those along the cystic duct, common bile duct, hepatic artery, and portal vein.
N2: The cancer has spread lymph nodes in the abdomen that are further away from the gallbladder, such as the lymph nodes lying along the aorta (periaortic), the vena cava (pericaval), the superior mesenteric artery, and the celiac artery.
M groups for gallbladder cancer
M0: The cancer has not spread to tissues or organs far away from the gallbladder.
M1: The cancer has spread to tissues or organs far away from the gallbladder.
TNM stage grouping for gallbladder cancer
Once the 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) to stage IV (the most advanced). Some stages are subdivided with letters.
Stage 0: Tis, N0, M0: There is a small cancer only in the epithelial layer of the gallbladder. It has not spread outside of the gallbladder.
Stage I: T1 (a or b), N0, M0: The tumor has grown into the lamina propria (T1a) or the muscle layer (T1b). It has not spread outside of the gallbladder.
Stage II: T2, N0, M0: The tumor has grown into the perimuscular fibrous tissue (T2). It has not spread outside of the gallbladder.
Stage IIIA: T3, N0, M0: The tumor extends through the serosa layer and/or directly grows into the liver and/or one other nearby structure (T3). It has not spread to lymph nodes or to tissues or organs far away from the gallbladder.
Stage IIIB: T1 to T3, N1, M0: The tumor has spread to nearby lymph nodes (N1), but it has not invaded the main blood vessels leading into the liver or reached more than one nearby organ other than the liver. It has not spread to tissues or organs far away from the gallbladder.
Stage IVA: T4, N0 or N1, M0: The tumor invades the main blood vessels leading into the liver or has reached more than one nearby organ other than the liver (T4). It may or may not have spread to nearby lymph nodes. It has not spread to tissues or organs far away from the gallbladder.
Stage IVB: Either of the following is true:
Any T, N2, M0: The main tumor may or may not have grown outside the gallbladder. It has spread to lymph nodes further away from the gallbladder (N2). It has not spread to tissues or organs far away from the gallbladder.
Any T, any N, M1: The main tumor may or may not have grown outside the gallbladder. It may or may not have spread to lymph nodes. The tumor has spread to tissues or organs far away from the gallbladder (M1).
Grading gallbladder cancer
Another factor that can affect the patient's outlook (prognosis) is the grade of the cancer. The grade describes how closely the cancer resembles normal gallbladder tissue when looked at under a microscope.
The scale used for grading gallbladder cancers goes from G1 (where the cancer looks much like normal gallbladder tissue) to G4 (where the cancer looks very abnormal). The grades G2 and G3 fall somewhere in between.
Typically, low-grade cancers are less likely to grow and spread quickly than high-grade cancers, and tend to have a more favorable outlook. Intermediate grade cancers have an appearance and prognosis between that of low- and high-grade cancers.
Last Medical Review: 04/30/2012
Last Revised: 01/18/2013