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GISTs are most common mesenchymal tumors of the gut but they account for less than one percent of all gastrointestinal tumors. GIST is a tumor of the special cells present in the wall of the gastrointestinal tract. These cells are called Interstitial cells of Cajal. These cells regulate the function and movements of the gut and are sometimes also called the pacemaker of gut.
Epidemiologically, GISTs are rare tumors. Only about 5000 new cases of GISTs are diagnosed every year in United States. Most of the tumors are smaller than four centimers in diameter, and are asymptomatic when they are diagnosed. A lot of the cases are discovered incidentally during radiological and endoscopic studies for any other GI tract abnormality. GISTs range from small benign tumors to metastatic malignant cancers.
GISTs: Clinical Presentation
Most GIST cases present during old age. The incidence of GISTs is almost equal in both genders. These tumors usually form a mass inside the gut which is responsible for most of the signs and symptoms. The clinical presentation of these tumors is as follows:
- A vague and nonspecific discomfort or pain in the abdomen is the most common symptom of GISTs
- Early satiety, which means a sensation of fullness after eating a small quantity of food
- Rarely, a GIST can be felt as a mass inside the abdomen. This mass is usually palpable on examination
- These tumors may bleed inside the gut. This may manifest as fatigue, malaise and shortness of breath
- In rare cases, a tumor may perforate the wall of the gut which results in the leakage of gut contents inside the abdominal cavity, leading to peritonitis
Gastrointestinal stromal tumors can also cause obstruction of the gut depending on their growth pattern. A tumor that is growing towards the lumen of the gut is more likely to block the gut. The symptoms of gut obstruction depend on the site of obstruction:
- A tumor in the esophagus may cause difficulty in swallowing, which is also called dysphagia
- A GIST in the colon or rectum may cause constipation
- A tumor in the duodenum may block the passage of bile and cause obstructive jaundice
The symptoms of GISTs vary in each patient depending on the size and site of the tumor. The diameter of gastrointestinal stromal tumors varies from one centimeter to as large as 40 centimeters. The most common location of these tumors is the stomach, which accounts for 60 to 70 percent of all cases. The small intestine is the second most common site of occurrence (20 to 30 percent). It is less common in the rest of the gastrointestinal tract.
GISTs are clinically and histologically diverse tumors. Some of them are indolent and slow-growing benign tumors while others are aggressive malignant carcinomas. For the same reason staging and grading is very important while making a diagnosis. The stage and grade of these tumors affect the clinical behaviour, treatment outcome and survival rates.
The survival rate is also variable in these cases. It depends on the stage of the tumor at the time of diagnosis and whether the tumor is benign or cancerous. Benign tumors have a very high survival rate. As with many other tumors, early detection results in a very high survival rate. Since this tumor has vague and nonspecific symptoms, they are usually diagnosed when they have grown to a very large size. The five year survival rate after diagnosis ranges from 38 to 60 percent.