Gastrointestinal Stromal Tumors (GISTS) comprise only 3% of all gastric malignancies and arise from mesenchymal components of the gastric wall. The median age at diagnosis is 60 years, with a slight male predominance. GISTs frequently display prominent extraluminal growth and can attain large sizes before becoming symptomatic.
- Presentation can be varied and includes asymptomatic masses found incidentally on physical exam or radiographic studies, vague abdominal pain and discomfort secondary to mass effect, and GI hemorrhage as a result of necrosis of overlying mucosa. Diagnosis is made by endoscopy and fine needle aspiration biopsy. GISTs are graded according to tumor size and histologic frequency of mitoses. Staging is accomplished by CT of abdomen/pelvis and chest x-ray.
- Treatment is open or laparoscopic surgical resection with 2-cm margins of grossly normal gastric wall to ensure negative histologic margins. En bloc resection of any structures involved by local invasion should be attempted, although lymphadenectomy is not indicated because lymph node metastases are rare. Metastasis occurs by hematogenous route, and hepatic involvement is common, as is local recurrence after resection. GISTs are not radiosensitive nor responsive to traditional chemotherapy. However, most GISTs express the c-kit receptor, a tyrosine kinase that acts as a growth factor receptor. Imatinib mesylate (Gleevec™) is a small-molecule inhibitor of the c-kit receptor that has become first-line therapy for metastatic or recurrent GIST. Approximately 60% of patients experience a partial response, and when maximal response is achieved, surgical therapy should be considered for patients in whom all gross disease can be removed.