<s>[INST] context: • GISTs: MC mesenchymal tumor of the GI tract
• MC primary site for GIST: Stomach (60–70%) > small bowel (20–25%) > colorectum and esophagus (5% each).
• Most GISTs are positive for CD-117 (95%), BCL-2 (80%), CD-34 (70%)
• Types: Spindle cell (70%) and Epitheloid (30%)
Pathology:
• Arise from the muscularis propria and most likely originate from the cells of Cajal
• Expression of the receptor tyrosine kinase KIT (CD 117), 5% express platelet derived growth factor receptor alpha (PDGFRA).
• PDGFRA mutations in GIST appear to confer a very favorable prognosis with low risk of recurrence.
• Spindle cell pattern (70%) of GIST is more common than epitheloid or round cell pattern (30%).
• New tumor markers of GIST: DOG-1 (discovered on GIST-1) and protein kinase C-theta
Clinical features:
• Patients usually present after the fourth decade, with the mean age of 60 years at diagnosis.
• MC presentations of gastric GISTs: GI bleeding and pain or dyspepsia.
Carney triad
• Association of extra-adrenal paragangliomas, pulmonary chondromas and multifocal GIST
Diagnosis:
• CT: IOC for evaluation of primary tumor and accurate staging
• PET-CT: Gold standard for recurrent GIST
• Percutaneous or endoscopic biopsy should only be performed if the results would obviate the need for surgeryQ.
Treatment:
• Bleeding manifestation is the MC indication for surgery.
• GIST should be treated with segmental resectionQ (margins of 1cm)
• LN metastasis are uncommon, regional lymphadenectomy is not recommended
• Intraoperative incisional biopsy prior to resection should be avoided, because it risks tumor spillage
• Imatinib (selective inhibitor of type 3 tyrosine kinase KIT), is approved for use in CD117-positive unresectable and metastatic GISTs.
• Functional imaging of GIST with 18FDG-PET scanning represents a useful diagnostic modality for early-response assessment with imatinib therapy.
• Sunitinib is used in imatinib-refractory disease.
Prognosis:
• Tumor size is a predominant factor for survival in surgical series for primary GIST.
• MC sites of disease failure after complete resection: Liver, omentum or peritoneal cavity.
• Half to two third primaries will have disease failure within the liver and nearly 40% will have liver as the only site of failure. Generally hepatic involvement is multifocal.
• Median time to recurrence after resection of primary GIST is 2 years. [/INST] question: Treatment of Zollinger Ellison syndrome - | options: A: Total gastrectomy with removal of tumour B: Partial gastrectomy C: Excision of tumour alone D: H2, receptor antogonist | answer: C </s>