Definition

Gastrointestinal Stromal Tumor (GIST) is a type of tumor characterized by abnormal and excessive growth of cells in the soft tissues of the digestive tract. Soft tissue refers to the supportive and connective tissues in various organs, such as fat cells, muscles, nerves, tendons, joints, vessels, and lymph vessels.

Gastrointestinal Stromal Tumor (GIST) can manifest throughout the digestive tract, affecting areas such as the esophagus, stomach, small intestine, and large intestine. The majority of cases occur in the stomach, with occasional instances in the small intestine. GIST in the esophagus, bowel, and rectum is less common. These tumors originate from cells that are part of the autonomic nervous system, located throughout the walls of the digestive tract. The nerve cells play a role in coordinating muscle movements for the digestion of food.

GISTs can be either malignant (cancerous) or benign. Malignant tumors have the potential to grow and spread to other parts of the body, while benign tumors may grow but do not spread to other organs. GISTs can occur at any age but are more commonly found in individuals aged 50-70 years, with rare occurrences in people under 40 years old.

Causes

Under normal conditions, all cells undergo a cycle of growth, division, and programmed death to maintain the body's health and proper functioning. However, at times, this process can become disrupted, leading to uncontrolled cell growth and division when cells should naturally die. When cell growth becomes uncontrollable, it results in the accumulation of mass known as a tumor. In the case of GIST, this occurs when the cells lining the digestive tract, specifically the interstitial cells of Cajal (ICC), undergo uncontrolled growth and division. The ICC serves the function of signaling the muscles in the digestive tract to contract, facilitating the movement of food and liquids through the digestive system.

The exact cause of Gastrointestinal Stromal Tumor (GIST) is still not fully understood, but it appears to be related to mutations in the expression of the KIT protein or the PDGFRA gene. These mutations may lead to accelerated cell growth and uncontrolled division. The reasons behind the occurrence of mutations in these genes are still not known.

Risk factor

The majority of Gastrointestinal Stromal Tumor (GIST) cases grow sporadically, meaning they occur without clear known causes. However, certain factors can increase the risk of GIST, including:

• Age over 50 years: GIST is more common in individuals aged over 50. While this tumor can occur at any age, it is rarer in individuals younger than 40.
• Gender: GIST is more common in men than in women.
• Genetic syndrome: Although GIST is rarely inherited within families, having a family history of GIST does not necessarily increase the risk of the disease. However, certain inherited genetic syndromes can elevate the risk of GIST, such as neurofibromatosis type 1 (NF1) and Carney-Stratakis dyad. A non-inherited syndrome called Carney triad can also increase the risk of GIST.

Symptoms

Gastrointestinal Stromal Tumor (GIST) typically grows in empty spaces within the digestive tract, often resulting in symptoms that may not directly manifest unless the tumor is located in a specific area or reaches a certain size. Small tumors may not exhibit any noticeable symptoms and are often discovered incidentally while investigating other health issues.

Gastrointestinal Stromal Tumor (GIST) tends to be a fragile and easily bleeding tumor, often becoming evident when it causes bleeding in the digestive tract. The signs and symptoms of bleeding depend on the speed of the bleeding and the location of the tumor, such as:

• Blood in vomit, indicating bleeding in the esophagus or stomach.
• Black and tarry stools are a result of bleeding in the stomach or small intestine.
• Bright red stools with fresh blood, suggest bleeding in the large intestine.
• In cases of slow bleeding, there may be no immediate symptoms of blood in vomit or changes in feces. However, over time, gradual bleeding can lead to anemia, making the individual feel weak and tired."

Other symptoms of GIST are:

• Abdominal pain
• Mass or swollen abdomen
• Nausea and vomiting
• Easy to feel full even though eating a small portion
• Loss of appetite
• Weight loss
• Swallowing difficulty (because of esophageal tumor)

Diagnosis

To diagnose GIST, the doctor will conduct a thorough history-taking, including inquiries about health history, symptoms, risk factors, family history, and other medical conditions. A physical examination will also be performed to gather information about signs of tumors, such as abdominal mass, and assess overall health.

If the doctor suspects GIST, several tests can be conducted to aid in the diagnosis. These tests include:

• CT or CAT scan (Computerized Tomography Scan): This imaging technique combines X-rays and computer technology to visualize cross-sectional slices of body organs.
• MRI SCAN (Magnetic Resonance Imaging): This method uses radio waves and a magnetic field to create detailed images.
• Upper Gastrointestinal Tract Endoscopy: This involves using a thin cable with a lamp and camera, inserted through the mouth to the upper digestive organs for visual examination.
• Ultrasonography Endoscopy: This procedure combines endoscopy with the use of ultrasound waves to create a sonogram, providing an image of the tissue within the body.
• Endoscopic Ultrasound Fine-Needle Aspiration (EUS-FNA): This procedure involves endoscopy with a thin needle attached. During this procedure, the doctor takes a tissue sample from the tumor for a biopsy. The biopsy sample is then examined under a microscope by a pathologist to determine if the tumor is indeed a Gastrointestinal Stromal Tumor (GIST).

If Gastrointestinal Stromal Tumor (GIST) is diagnosed, the doctor will recommend further tests to determine if cancer cells have spread to other organs. These tests may include a CAT scan, MRI, chest imaging, or a PET (Positron Emission Tomography) scan. During a PET scan, a small amount of radioactive glucose is injected into the vein. The imaging machine scans the body, capturing images where cancerous cells, which absorb more glucose, appear brighter.

Management

The management of GIST depends on whether the tumor can be removed by surgery or if cancer cells have spread to other parts of the body. Here are some management options for GIST:

• Surgery: If the GIST has not spread, the doctor may perform surgery to remove the tumor and surrounding tissue. A laparoscope, a tool resembling a thin cable, may be used to make small incisions and extract tissue.
• Targeted Drug Therapy: This therapy targets specific genes. Drugs such as tyrosine kinase inhibitors (TKIs) may be prescribed to halt the signal for tumor growth. This medication is less harmful to healthy cells compared to chemotherapy or radiation.
• Observation: The doctor may choose to observe and wait with caution. Specific therapy may not be given until there are changes in symptoms.
• Supportive Therapy: In cases where GIST worsens or there are side effects from the given therapy, supportive therapy may be needed to improve the individual's quality of life.

Complications

GIST occurs in the digestive tract and can, throughout the disease, grow and spread to nearby organs or structures. GIST often spreads to the liver and peritoneum (the layer in the abdominal cavity) but rarely to the lymph nodes near the tumor. The spread of the disease is correlated with the 5-year survival rates.

According to the National Cancer Institute, the 5-year survival rate for GIST is 83%, indicating that 83% of individuals diagnosed with GIST survive for at least 5 years after diagnosis. The survival rate is higher if GIST is localized and has not spread to other areas of the body, reaching 93%. However, if the tumor has spread to distant locations, the survival rate drops to 55%.

Prevention

While certain lifestyle changes, such as quitting alcohol, stopping smoking, or maintaining an ideal body weight, can reduce the risk of some cancers, there are no known lifestyle factors associated with Gastrointestinal Stromal Tumor (GIST) risk. This makes it unclear how to prevent GIST through lifestyle modifications.

When to see a doctor?

GIST symptoms, such as abdominal pain, vomiting, and weakness, often overlap with those of other diseases. If you experience these symptoms persistently, it is crucial to consult with a doctor to identify the underlying causes.

If you have risk factors for GIST or other conditions that may influence the growth of GIST, ensure that you communicate this information to your doctors. Symptoms like blood in vomit or changes in feces color, turning black or containing fresh blood, are indicative of digestive tract bleeding. If you observe these symptoms, consult with your doctor promptly, as they could be associated with GIST.