Staging
The most commonly used system for staging gastrointestinal stromal tumors (GISTs) is the TNM system developed by the American Joint Committee on Cancer (AJCC), with the most recent update implemented in 2018. This system evaluates four key factors:
Tumor size (T): How large is the primary tumor?
Lymph node involvement (N): Has the cancer spread to nearby lymph nodes? (This is rare in GISTs.)
Metastasis (M): Has the cancer spread to distant parts of the body? (Common sites of spread include the liver, lungs, bones, and the peritoneum—the lining of the abdominal cavity.)
Mitotic rate: This laboratory measurement reflects how quickly the tumor cells are dividing. It is classified as either low or high, with a low mitotic rate indicating a more favorable prognosis.
Stage IA
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Description
- The tumor is:
No more than 2 cm across (T1) OR
Larger than 2 cm but not more than 5 cm across (T2).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is low.
Treatment
- Surgery; rarely, some very small GISTs found by chance may be serially observed.
Stage IB
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Description
- The tumor is larger than 5 cm but not more than 10 cm across (T3).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is low.Low grade tumor that is between 5 cm and 10 cm in diameter
Treatment
- Surgery; targeted therapy before or after surgery may be considered.
Stage II
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Description
- The tumor is no more than 2 cm across (T1).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is high.High grade tumor that is smaller than 5 cm in diameter. Cancer has not spread to lymph nodes or other parts of the body.
- OR
- The tumor is larger than 2 cm, but not more than 5 cm across (T2).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is high.
- OR
- The tumor is larger than 10 cm across (T4).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is low.
- OR
Treatment
- Surgery; targeted therapy before or after surgery may be considered.
Stage IIIA
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Description
- The tumor is larger than 10 cm across (T4).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0).
- OR
- The tumor is larger than 2 cm but not more than 5 cm across (T2).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is high.
Treatment
- Surgery; targeted therapy before or after surgery may be considered.
Stage IIIB
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Description
- The tumor is larger than 5 cm but not more than 10 cm across (T3).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is high.
- OR
- The tumor is larger than 10 cm across (T4).
The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0). The mitotic rate is high.
- OR
- The tumor is any size (Any T) AND it has spread to nearby lymph nodes (N1).
The cancer has not spread to distant sites (M0). The mitotic rate can be low or high.
Treatment
- Surgery; targeted therapy before or after surgery may be considered.
Stage IV
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Description
- The tumor is any size (Any T) AND it might or might not have spread to nearby lymph nodes (Any N).
The cancer has spread to distant parts of the body (M1). The mitotic rate can be low or high.
Treatment
- Targeted therapy, clinical trials, with or without surgery to remove operable metastases.
