الفهرس 
Epidemiology of Gastrointestinal Stromal TumorsOnly 14 pages are availabe for public view
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Abstract
Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Although their incidence is low, these tumors make up a unique entity based on their molecular pathogenesis, immuno-histochemical stainig and responsiveness to targeted therapy (Antonescu, 2008).
In the past, some tumors were thought to start in the muscle layer of the gastrointestinal tract and some were thought to start in nerve cells. This is because the tumor cells look like muscle or nerve cell under the microscope. They were often thought to be related to sarcomas. However, it is now known that these tumors are in fact not true muscle or nerve tumors. Most doctors believe they start in special cells found in the wall of the gastrointestinal tract called the interstitial cells of Cajal (ICCs) or in very early cells that can develop into the interstitial cells of Cajal (Mazur et al., 1998).
The interstitial cells of Cajal are part of the autonomic nervous system which send signals to the gastrointestinal tract. Some have called these cells the ”pacemakers” of the gastrointestinal tract. The nerve signals they send cause muscles of the digestive organs to contract which help to move food and liquid through the gastrointestinal tract (Kindblom et al., 1998).
Gastrointestinal stromal tumors can occur anywhere in the gastrointestinal tract. They are submucosal lesions which most frequently grow endophytically in parallel with the lumen of the affected structure. They may also manifest as exophytic extraluminal excrescences (Dematteo, 2002).
These tumors have been reported ranging in size from smaller than 1 cm to as large as 40 cm in diameter and vary in malignant potential ranging from small accidentally detected tumors with an excellent outcome to aggressive sarcomas (Galateros et al., 2008).
Approximately (50-70%) of gastrointestinal stromal tumors originate in the stomach. The small intestine is the second most common location with (20-30%) of gastrointestinal stromal tumors arising from the jejunoileum. Less frequent sites of occurrence include the colon and rectum (5-15%) and oesophagus (<5%). Primary omental or mesenteric gastrointestinal stromal tumors have been reported but are very rare (Belinsky et al., 2008).
Until recently gastrointestinal stromal tumors were known for being resistant to chemotherapy with a success rate less than 5%. However, new targeted therapies have emerged that provide a new hope for treatment of these patients (Belinsky et al., 2008).