الفهرس 
Emberiological BackgroundOnly 14 pages are availabe for public view
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Abstract
Gastrointestinal stromal tumour (GIST) is a rare disease, and data concerning its worldwide prevalence are lacking. In general, it constitutes 1-3% of all gastrointestinal malignancies. GIST is not more prevalent in either sex. Onset can occur at any age, but the typical age of onset is in the sixth to seventh decades of life.
GISTs are the most common mesenchymal neoplasm of the gastrointestinal tract. They are defined by the expression of KIT (CD117) in the tumour cells.
Recent studies suggest that GIST may originate from the interstitial cells of Cajal (ICCs) These cells are distributed along the gastrointestinal tract and play a role in the control of gut motility. The ICCs exhibit both myeloid and neural features and express the c-kit proto-oncogene receptor.
Histologically GISTs vary from cellular spindle cell tumours to epithelioid ones. By definition they are CD117 positive, although positivity for nestin and CD34 is also common but not specific.
The number of mitotic figures is the most accepted index for grade classification, although other histologic parameters, such as cellularity, atypia, and necrosis, are also taken into consideration. Predictive of malignancy are mitotic rate over 5 per 10 high-power fields (HPFs) or size over 5 cm. However, tumours with low mitotic index can also metastasize, and gastric tumours are commonly less aggressive than the intestinal ones.
GISTs are typically diagnosed as solitary lesions, although in rare cases, multiple lesions can be found. These tumours can grow intraluminally or extraluminally, toward the abdominal cavity and adjacent structures. When the growth pattern is extraluminal, patients can be symptom free for a long time and present with very large exogastric masses.
Distant metastases tend to appear late in the course of the disease in most cases. In contrast to other soft tissue tumours, the common metastatic sites of GISTs are the liver and peritoneum. Lymph node involvement is rare and is in the range of 0-8%.
Abdominal CT scanning with intravenous and oral contrast material is a necessary step in the evaluation of patients with GISTs. CT scanning can also be used to evaluate tumour invasion to adjacent structures and the presence of intra- abdominal metastasis.
Endoscopic ultrasonography (EUS) is a valuable tool in the diagnosis and preoperative assessment of GISTs. It can demonstrate the submucosal location of the tumour and can define its size, borders, and echoic pattern. Diagnosis can often be made using ultrasonographic-guided biopsy. However, the histology obtained can demonstrate a spindle cell tumour but can hardly differentiate between benign and malignant forms.
Surgical resection is the treatment of choice and offers the only chance for cure. The main operative principle is resection of the tumour with clear margins, preferably about 2 cm wide. The goals of pharmacotherapy are to induce remission, reduce morbidity, and prevent complications.
Follow-up care after curative operations is important because certain patients with recurrent disease may benefit from second surgical intervention and from systemic therapy with imatinib mesylate or chemotherapy for unresectable and metastatic disease. Follow-up includes physical examination and periodical gastroscopies and CT scanning.
In general, long-term survival for malignant GIST after a curative-intent surgery typically correlated inversely with tumour size and histologic grade.
Gastrointestinal stromal tumour (GIST) is a rare disease, and data concerning its worldwide prevalence are lacking. In general, it constitutes 1-3% of all gastrointestinal malignancies. GIST is not more prevalent in either sex. Onset can occur at any age, but the typical age of onset is in the sixth to seventh decades of life.
GISTs are the most common mesenchymal neoplasm of the gastrointestinal tract. They are defined by the expression of KIT (CD117) in the tumour cells.
Recent studies suggest that GIST may originate from the interstitial cells of Cajal (ICCs) These cells are distributed along the gastrointestinal tract and play a role in the control of gut motility. The ICCs exhibit both myeloid and neural features and express the c-kit proto-oncogene receptor.
Histologically GISTs vary from cellular spindle cell tumours to epithelioid ones. By definition they are CD117 positive, although positivity for nestin and CD34 is also common but not specific.
The number of mitotic figures is the most accepted index for grade classification, although other histologic parameters, such as cellularity, atypia, and necrosis, are also taken into consideration. Predictive of malignancy are mitotic rate over 5 per 10 high-power fields (HPFs) or size over 5 cm. However, tumours with low mitotic index can also metastasize, and gastric tumours are commonly less aggressive than the intestinal ones.
GISTs are typically diagnosed as solitary lesions, although in rare cases, multiple lesions can be found. These tumours can grow intraluminally or extraluminally, toward the abdominal cavity and adjacent structures. When the growth pattern is extraluminal, patients can be symptom free for a long time and present with very large exogastric masses.
Distant metastases tend to appear late in the course of the disease in most cases. In contrast to other soft tissue tumours, the common metastatic sites of GISTs are the liver and peritoneum. Lymph node involvement is rare and is in the range of 0-8%.
Abdominal CT scanning with intravenous and oral contrast material is a necessary step in the evaluation of patients with GISTs. CT scanning can also be used to evaluate tumour invasion to adjacent structures and the presence of intra- abdominal metastasis.
Endoscopic ultrasonography (EUS) is a valuable tool in the diagnosis and preoperative assessment of GISTs. It can demonstrate the submucosal location of the tumour and can define its size, borders, and echoic pattern. Diagnosis can often be made using ultrasonographic-guided biopsy. However, the histology obtained can demonstrate a spindle cell tumour but can hardly differentiate between benign and malignant forms.
Surgical resection is the treatment of choice and offers the only chance for cure. The main operative principle is resection of the tumour with clear margins, preferably about 2 cm wide. The goals of pharmacotherapy are to induce remission, reduce morbidity, and prevent complications.
Follow-up care after curative operations is important because certain patients with recurrent disease may benefit from second surgical intervention and from systemic therapy with imatinib mesylate or chemotherapy for unresectable and metastatic disease. Follow-up includes physical examination and periodical gastroscopies and CT scanning.
In general, long-term survival for malignant GIST after a curative-intent surgery typically correlated inversely with tumour size and histologic grade.