Gastrointestinal Stromal Tumor (GIST)

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Early Detection, Diagnosis, and Staging TOPICS

How are gastrointestinal stromal tumors staged?

The stage of a cancer describes how far the cancer has spread. For many cancers, the stage is an important factor in selecting treatment options and in predicting a person’s prognosis (outlook). To help stage the tumor, doctors use the results of physical exams and imaging, endoscopy, or other tests, such as those described in “How are gastrointestinal stromal tumors diagnosed?

AJCC TNM staging system

Doctors use a staging system to describe the extent of spread of most types of cancer, including gastrointestinal stromal tumors (GISTs). The most common system used is the TNM system of the American Joint Committee on Cancer (AJCC). This system is based on 4 key pieces of information:

  • T describes the size of the primary tumor, measured in centimeters (cm).
  • N describes whether the cancer has spread to nearby (regional) lymph nodes (which is very rare for GISTs).
  • M indicates whether the cancer has metastasized (spread) to other organs of the body. If a GIST does spread, most often it is within the abdomen, such as to the liver. Less often, it may spread to the lungs and bones.
  • The mitotic rate is a measure of how fast the cancer cells are growing and dividing. It is described as either low or high. A low mitotic rate predicts a better outcome.

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.

T categories for GIST

TX: The primary (main) tumor cannot be assessed.

T0: No signs of a primary tumor.

T1: The tumor is 2 cm or less across (about 4/5 of an inch).

T2: The tumor is larger than 2 cm across but not larger than 5 cm (about 2 inches).

T3: The tumor is larger than 5 cm across but not larger than 10 cm (about 4 inches).

T4: The tumor is larger than 10 cm across.

N categories for GIST

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 for GIST

M0: The cancer has not spread (metastasized) to distant organs or sites.

M1: The cancer has spread to distant organs or sites (like the liver or the lungs).

Stage grouping

Once the T, N, and M categories have been determined, this information is combined, along with the mitotic rate, in a process called stage grouping. The overall stage is expressed in Roman numerals from I (the least advanced) to IV (the most advanced). The stage grouping depends on where the tumor starts.

GIST that starts in the stomach or the omentum*

*The omentum is an apron-like layer of fatty tissue that hangs over the organs in the abdomen

Stage IA: T1 or T2, N0, M0, low mitotic rate: The tumor is no larger than 5 cm across (T1 or T2). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.

Stage IB: T3, N0, M0, low mitotic rate: The tumor is larger than 5 cm but not larger than 10 cm across (T3). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.

Stage II: One of the following applies:

    T1 or T2, N0, M0, high mitotic rate: The tumor is no larger than 5 cm across (T1 or T2). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is high.

    T4, N0, M0, low mitotic rate: The tumor is larger than 10 cm across (T4). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.

Stage IIIA: T3, N0, M0, high mitotic rate: The tumor is larger than 5 cm but not larger than 10 cm across (T3). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is high.

Stage IIIB: T4, N0, M0, high mitotic rate: The tumor is larger than 10 cm across (T4). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is high.

Stage IV: One of the following applies:

    Any T, N1, M0, any mitotic rate: The tumor can be any size (any T) and the cancer has spread to nearby lymph nodes (N1). It has not spread to distant sites (M0). The tumor can have any mitotic rate.

    Any T, any N, M1, any mitotic rate: The tumor can be any size (any T) and it may or may not have spread to nearby lymph nodes (any N). The cancer has spread to distant sites, such as the liver or the lungs (M1). The tumor can have any mitotic rate.

GIST of the small intestine, esophagus, colon, rectum, or peritoneum**

**The peritoneum is a layer of tissue that lines the organs and walls of the abdomen.

Tumors in these locations are more likely to grow quickly than GISTs that start in the stomach.

Stage I: T1 or T2, N0, M0, low mitotic rate: The tumor is no larger than 5 cm across (T1 or T2). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.

Stage II: T3, N0, M0, low mitotic rate: The tumor is larger than 5 cm but not larger than 10 cm across (T3). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.

Stage IIIA: One of the following applies:

    T1, N0, M0, high mitotic rate: The tumor is no larger than 2 cm across (T1). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is high.

    T4, N0, M0, low mitotic rate: The tumor is larger than 10 cm across (T4). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is low.

Stage IIIB: T2 to T4, N0, M0, high mitotic rate: The tumor is larger than 2 cm across (T2 to T4). The cancer has not spread to nearby lymph nodes (N0) or distant sites (M0). The mitotic rate is high.

Stage IV: One of the following applies:

    Any T, N1, M0, any mitotic rate: The tumor can be any size (any T) and the cancer has spread to nearby lymph nodes (N1). It has not spread to distant sites (M0). The tumor can have any mitotic rate.

    Any T, any N, M1, any mitotic rate: The tumor can be any size (any T) and it may or may not have spread to nearby lymph nodes (any N). The cancer has spread to distant sites, such as the liver or the lungs (M1). The tumor can have any mitotic rate.

Resectable versus unresectable tumors

The AJCC staging system provides a detailed summary of how far a GIST has spread. But for treatment purposes, doctors are often more concerned about whether the tumor can be removed (resected) with surgery.

Whether or not a tumor is resectable depends on its size and location, whether it has spread to other parts of the body, and on if a person is healthy enough for surgery. Tumors that can clearly be removed are defined as resectable, while those that can’t be removed completely (because they have spread or for other reasons) are described as unresectable. In some cases, doctors may describe a tumor as marginally resectable if it’s not clear if it can be removed completely.

If a tumor is considered unresectable or marginally resectable when it is first found, treatments such as targeted therapy may be used first to try to shrink the tumor enough to make it resectable.


Last Medical Review: 12/11/2012
Last Revised: 02/26/2013