Gastrointestinal Stromal Tumor (GIST)
A tumor arising in the wall of the digestive tract
Quick Facts
- Type: Digestive tract (soft tissue) tumor
- Most common site: Stomach, then small intestine
- Arises from: Interstitial cells of Cajal (pacemaker cells)
- Key treatment: Surgery and targeted drug therapy
Overview
A gastrointestinal stromal tumor (GIST) is a tumor that grows in the wall of the digestive (gastrointestinal) tract. GISTs arise from specialized cells called the interstitial cells of Cajal, which act like pacemakers that help move food through the gut. This makes them different from the more common cancers that start in the inner lining of the digestive tract.
GISTs occur most often in the stomach, followed by the small intestine, but can develop anywhere along the digestive tract. They range from small, harmless growths found by chance to larger tumors that can grow and spread. A key feature of GISTs is that many are driven by specific gene changes that can be targeted with modern medicines, which has greatly improved treatment.
Symptoms
Small GISTs often cause no symptoms and may be found incidentally during tests for another reason. Larger tumors can cause:
- Vague abdominal discomfort, fullness, or a feeling of a mass
- Nausea, loss of appetite, or unintended weight loss
- Bleeding into the digestive tract, which may cause black or bloody stools, vomiting blood, or anemia and fatigue
- Abdominal pain
- Rarely, a blockage of the bowel
Vomiting blood, black or tarry stools, or sudden severe abdominal pain are emergencies and need immediate medical care.
Causes
GISTs develop when the interstitial cells of Cajal acquire gene changes that make them grow uncontrollably.
- KIT and PDGFRA gene changes: Most GISTs are driven by a change in one of these genes, which can often be targeted by specific drugs.
- Sporadic occurrence: The great majority arise by chance, not through inheritance.
- Inherited syndromes: Rarely, GISTs are part of inherited conditions, including a link with neurofibromatosis type 1.
GISTs are not contagious and are not caused by diet or lifestyle in any proven way.
Risk Factors
- Middle to older age (most are diagnosed in adults)
- Rare inherited syndromes that include GIST
- Neurofibromatosis type 1, which is associated with a higher chance of GIST
Most people with a GIST have no identifiable risk factor.
Diagnosis
Diagnosis usually involves imaging, endoscopy, and tissue testing.
- Endoscopy: A camera passed into the digestive tract can reveal a tumor in the stomach or intestine, sometimes with endoscopic ultrasound to assess depth.
- CT scan: To show the tumor's size and location and check for spread, most often to the liver or abdomen.
- Biopsy: A tissue sample to confirm the diagnosis.
- Molecular testing: Analysis of KIT and PDGFRA genes, which guides targeted treatment.
Treatment
Treatment depends on the tumor's size, location, and risk of spread, and on its gene changes.
- Surgery: The main treatment for tumors that can be removed, aiming to take out the GIST completely.
- Targeted therapy: Medicines such as imatinib block the signals from KIT or PDGFRA that drive the tumor; these are used for larger or spread tumors, sometimes before surgery to shrink the tumor, and after surgery to lower the risk of return.
- Active monitoring: Very small, low-risk GISTs found incidentally may simply be watched.
- Additional targeted drugs: Used if the tumor becomes resistant to the first medicine.
Treatment is individualized by a specialist team, and many people do well, especially when the tumor is found early.
Prevention
There is no known way to prevent GISTs, because they arise from gene changes in the digestive tract cells. The focus is on early detection and appropriate follow-up:
- Prompt evaluation of digestive symptoms such as bleeding, persistent discomfort, or unexplained anemia
- Specialist follow-up for people with inherited syndromes that include GIST
- Regular monitoring after treatment to detect any recurrence early
When to See a Doctor
See a doctor for persistent abdominal discomfort, unexplained weight loss, or signs of slow blood loss such as fatigue and pale skin. Seek emergency care immediately for:
- Vomiting blood or material that looks like coffee grounds
- Black, tarry, or bloody stools
- Sudden, severe abdominal pain
- Feeling faint, dizzy, or short of breath, which can signal significant bleeding
Frequently Asked Questions
What is a gastrointestinal stromal tumor?
A GIST is a tumor that grows in the wall of the digestive tract, most often the stomach or small intestine, arising from pacemaker cells that help move food through the gut. It differs from the more common cancers that start in the inner lining.
Are all GISTs cancerous?
GISTs vary from small, harmless growths to larger tumors that can grow and spread. Their behavior is assessed by size, location, and how quickly the cells divide, which helps guide whether and how to treat them.
How are GISTs treated?
Surgery to remove the tumor is the main treatment when possible. Targeted drugs such as imatinib, which block the genes driving the tumor, are used for larger or spread tumors and to lower the risk of recurrence, and have greatly improved outcomes.
What symptoms do GISTs cause?
Small GISTs often cause no symptoms. Larger ones can cause abdominal discomfort, fullness, weight loss, or bleeding into the gut, which may show up as black or bloody stools, vomiting blood, or anemia and fatigue.
When is a GIST an emergency?
Seek emergency care for vomiting blood, black or tarry stools, sudden severe abdominal pain, or feeling faint, as these can indicate significant internal bleeding or a bowel blockage.
References
- National Cancer Institute (NCI). Gastrointestinal Stromal Tumors Treatment.
- Mayo Clinic. GIST (gastrointestinal stromal tumor).
- MedlinePlus, U.S. National Library of Medicine. Gastrointestinal stromal tumor.
- American Cancer Society. Gastrointestinal Stromal Tumor (GIST).