Gastrointestinal stromal tumor
| Gastrointestinal stromal tumor | |
|---|---|
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| Histopathologic image of gastrointestinal stromal tumor of the stomach. Hematoxylin-eosin stain. | |
| Classification and external resources | |
| Specialty | Oncology |
| ICD-O | M8936/0 - M8936/3 |
| OMIM | 606764 |
| DiseasesDB | 33849 |
| MeSH | D046152 |
Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. GISTs arise in the smooth muscle pacemaker interstitial cell of Cajal, or similar cells. They are defined as tumors whose behavior is driven by mutations in the KIT gene (85%),PDGFRA gene (10%), or BRAF kinase (rare). 95% of GISTs positively for KIT (CD117). Most (66%) occur in the stomach and gastric GISTs have a lower malignant potential than tumors found elsewhere in the GI tract.
GIST was introduced as a diagnostic term in 1983. Until the late 1990s, many non-epithelial tumors of the gastrointestinal tract were called "gastrointestinal stromal tumors". Histopathologists were unable to specifically distinguish between types we now know to be dissimilar molecularly. Subsequently, CD34, and later CD117 were identified as markers that could distinguish the various types. Additionally, in the absence of specific therapy, the diagnostic categorization had only a limited influence on prognosis and therapy.
The understanding of GIST biology changed significantly with identification of the molecular basis of GIST, particularly c-KIT. Historically, literature reviews prior to the molecular definition of GIST, and for a short time thereafter, asserted that 70-80% of GISTs were benign. The identification of a molecular basis for GIST led to the exclusion of many tumors that had been considered as GIST previously, and also the incorporation of a much larger number of tumors that had been labeled as other types of sarcomas and undifferentiated carcinomas. For example, some previous diagnoses of stomach and small bowel leiomyosarcomas (malignant tumor of smooth muscle) would be reclassified as GISTs on the basis of immunohistochemical staining. All GIST tumors are now considered to have malignant potential, and no GIST tumor can be definitively classified as "benign". Hence, all GISTs are eligible for cancer staging in the AJCC (7th edition) / UICC. Nonetheless, different GISTs have different risk assessments of their tendency to recur or to metastasize, dependent on their site of origin, size, and number of mitotic figures.
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