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Gastrointestinal Stromal Tumor(GIST). This video enumerates the salient aspects of GIST including pathogenesis, morphological features, clinical features, and treatment aspects.


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Common mesenchymal tumor of GI Tract
Arises from the interstitial cells of Cajal within the myenteric plexus of the muscularis propria
Extragastrointestinal GIST: GIST arising outside of the gastrointestinal tract Common sites include -omentum, mesentery, retroperitoneum,pleura
Carney triad- a nonhereditary syndrome of GIST, paraganglioma, and pulmonary chondroma that occurs primarily in females.
GIST tumors can also be seen as a part of neurofibromatosis type 1.
Majority of GIST tumors have KIT or PDGFRA mutation. Both trigger the troskine kinase receptor phosporylation leading to cell growth proliferation and survival.
GISTs without mutated KIT or PDGFRA often have mutations in genes encoding components of the mitochondrial succinate dehydrogenase complex (SDHA, SDHB, SDHC, SDHD)cycle.
Mutations causing loss of succinate dehydrogenase function, are often inherited in the germline and confer an increased risk for GIST,pulmonary chondroma and paraganglioma (Carney-Stratakis syndrome).
Gross Findings:
-GISTs averages 5-6 cm with size varying from 0.5-40 cm in diameter.
-They usually form a solitary, well-circumscribed, fleshy mass.
-The overlying mucosa is frequently ulcerated, and the cut tumor surface has a fleshy, tan-pink, whorled appearance with occasional areas of haemorrhage, cystic changes.
-Metastases can form multiple serosal nodules throughout the peritoneal cavity or within the liver, but spread outside of the abdomen is uncommon.
GISTs are classified as:-
Spindle cell type : proliferation of thin spindle cells
Epithelioid type: proliferation of plumper, epithelial-appearing cells
Mixtures of the two patterns are common.
The most useful diagnostic markers are DOG1,KIT (CD117), which is immunohistochemically detectable in Cajal cells and 95% of gastric GISTs.
CD34, PDGFRa may also stain positive.
Negative for SMA(variable), S100
More common in 6th decade,males and females with almost equal incidence
Symptoms of GISTs at presentation are typically related to mass effects.
Mucosal ulceration can cause blood loss, and approximately half of individuals with GISTs present with anemia or related symptoms.
GISTs may also be discovered incidentally during radiologic imaging, endoscopy, or abdominal surgery performed for other reasons.
Complete surgical resection is the primary treatment for localized gastric GIST.
The prognosis correlates with tumor size, mitotic index, and location, with gastric GISTs being less aggressive than those arising in the small intestine.
Recurrence or metastasis is rare for gastric GISTs smaller than 5 cm but common for mitotically active tumors larger than 10 cm.
Tumors with mutations in KIT or PDGFRA often respond to the tyrosine kinase inhibitor imatinib, whereas tumors without these mutations are generally resistant.

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