Gastrointestinal Stromal Tumor (GIST)

Individuals with small gastrointestinal stromal tumors (GISTs) may be asymptomatic, depending on the growth rate of the tumor.¹ Therefore, GIST can be diagnosed as incidental findings when imaging is performed for other reasons. Usually, GIST is diagnosed when individuals have a medical work-up to determine the underlying cause of chronic anemia, fatigue, abdominal pain, or gastrointestinal bleeding.² 

Symptoms of GIST include:^1,2,3

• hematochezia or melena (fresh or old blood in the stools, respectively)
• hematemesis (vomiting blood)
• anemia
• fatigue 
• nausea
• vomiting
• abdominal pain
• loss of appetite/anorexia
• epigastric fullness and early satiety
• weight loss
• difficulty swallowing
• a palpable mass in the abdomen  
• bowel obstruction
• constipation

Gastrointestinal Bleeding

GISTs are fragile tumors with a tendency toward easy bleeding. Bleeding occurs due to pressure necrosis and perforation of the mucosal wall where the tumor develops, which causes a hemorrhaging of nearby blood vessels.⁴ Signs and symptoms of gastrointestinal bleeding depend on where the tumor is located and how fast the bleeding occurs. If the tumor is rapidly bleeding in the stomach or esophagus, the individual may vomit blood that looks like coffee grounds due to partial digestion. If the tumor is in the stomach or small intestine, rapid bleeding into the gastrointestinal (GI) tract may result in stools that are black and tarry from the blood which changes color from red to black as it takes a longer time to exit the GI tract from these locations. If the tumor is in the large intestine or rectum, rapid bleeding would produce stools with fresh, red blood. If the bleeding is slow, often the individual will not have any signs of outward bleeding, rather, they develop chronic anemia over time.³

The most common clinical manifestation of GIST in about 40% to 65% of patients involves upper GI bleeding, resulting in hematemesis or melena.⁴ 

Anemia

Anemia that is GIST-related is caused by loss of blood from a slow-bleeding tumor into the GI tract. Anemia is a condition in which the body lacks an adequate amount of red blood cells necessary to transport oxygen to the tissues of the body. Anemia can be diagnosed following a complete blood count (CBC) indicating a lower-than-normal red blood cell count. The reference range for a normal red blood cell count for men is 4.5 million to 5.9 million cells/mcL. Less than 4.5 million red blood cells/mcL indicates anemia in men.⁶ For women, the reference range for a normal red blood cell count is 4.1 million to 5.1 million cells/mcL.⁵ Less than 4 million red blood cells/mcL indicates anemia in women.⁶ 

Fatigue

Fatigue, or the feeling of being tired and weak, is due to the anemia from the slow-bleeding GIST which causes the low red blood cell count.² When an individual has anemia, their body has to work much harder than normal to produce energy via the Krebs Cycle and the electron transport chain, which ultimately requires the oxygen that is carried by the red blood cells throughout the body.⁷

Nausea and Vomiting

Nausea and vomiting result from the irritation of nerve endings in the stomach and/or duodenum. These nerve endings send messages which then stimulate the regions of the brain that control nausea and vomiting.⁸ In GIST, the mechanical pressure of the tumor growth or accumulation of blood from a bleeding tumor pushing into these nerve endings may potentially aggravate these symptoms.  

Abdominal Pain

Due to their fragility, GISTs may rupture which leads to formation of holes or perforations in the GI tract wall.³ This causes severe abdominal pain and may require emergency surgery. Mechanical nociceptors (pain receptors) within the GI tract may also be activated due to the mechanical pressure of the tumor pushing into them, thus triggering a visceral pain sensation.⁹ 

Appetite Changes Leading to Weight Loss

If a large GIST or multiple GISTs are present in the stomach or small intestine, this may limit the amount of food that can be processed at a given point in time due to lack of space available for the stomach to expand during digestion. Eating even a small amount of food, depending on the size and location of the tumor, may trigger a feeling of early satiety. If eating a meal is accompanied by anxiety, nausea, vomiting, or abdominal pain, the individual may develop a corresponding anorexia or loss of appetite to avoid these unpleasant symptoms which results in unintended weight loss.⁴ Cancer medications used to treat GIST may produce side effects such as diarrhea, nausea, dehydration, and vomiting, which can also lead to weight loss.¹⁰ 

Difficulty Swallowing

If an individual has an esophageal GIST, this may lead to swallowing difficulties due to mechanical obstruction or deformation of the smooth muscle of the esophagus.³

Bowel Obstruction/Constipation

Large GISTs may cause obstruction, or blockage of the passage of food through the stomach and/or intestines, causing significant abdominal pain and vomiting.³ Obstruction may result from the intraluminal growth of a tumor located on the inside of the GI tract (endophytic) or from the inward compression of the GI lumen from tumors on the outside of the GI tract (exophytic).⁴ Associated obstructive symptoms are dependent on tumor location. Esophageal obstruction may result in dysphagia. Tumors in the colon and rectum may cause constipation. The obstructive pressure of a duodenal tumor may cause jaundice.⁴ GISTs that are large enough may be detectable through palpation on examination of the abdomen.

References

1. Gastrointestinal stromal tumor (GIST): overview. Mayo Clinic. Accessed June 18, 2021.
2. Gastrointestinal stromal tumor (GIST): symptoms and signs. Cancer.Net. Accessed June 15, 2021.
3. Signs and symptoms of gastrointestinal stromal tumors. Cancer. Org. Accessed June 15, 2021.
4. Gastrointestinal stromal tumors (GISTs) clinical presentation: history, physical examination. Medscape. Accessed June 15, 2021.
5. Complete blood count (CBC) test. WebMD. Accessed June 17, 2021.
6. Evaluation of anemia. Merck Manual Professional Version. Accessed June 23, 2021. 
7. How does the body produce energy? Metabolics. Accessed June 15, 2021.
8. Nausea: pathology. Encyclopedia Britannica. Accessed June 17, 2021.
9. Nociception. Physiopedia. Accessed June 17, 2021.
10. Coping with weight change. LifeRaftGroup. Accessed June 23, 2021.

Article reviewed by Eleni Fitsiou Ph.D., on July 1, 2021.

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Maria Arini Lopez, PT, DPT, CSCS, CMTPT, CIMT

Maria Arini Lopez, PT, DPT, CSCS, CMTPT, CIMT is a freelance medical writer and Doctor of Physical Therapy from Maryland. She has expertise in the therapeutic areas of orthopedics, neurology, chronic pain, gastrointestinal dysfunctions, and rare diseases especially Ehlers Danlos Syndrome.