An update on gastrointestinal stromal tumors (GISTs) with a focus on extragastrointestinal stromal tumors (EGISTs)

Gastrointestinal stromal tumors (GISTs) originate from mesenchymal cells and account for ∼1% of primary malignant tumors in the digestive system. They are diagnosed based on characteristic immunohistochemical staining pattern, including CD117 and DOG1, as well as genetic analysis for mutations in the KIT and platelet-derived growth factor receptor α genes. Extragastrointestinal stromal tumors (EGISTs) share very similar morphology with GISTs but arise outside the gastrointestinal tract. The most common locations for EGISTs are the omentum, mesentery, retroperitoneum, and pancreas, followed by the liver, vagina, and prostate. The mean age of presentation of these tumors is in the sixth decade of life and tumor dimensions at different locations typically range from 7 to 15.8 cm. Most of these tumors are unifocal and of the spindle cell type. GISTs generally have a better prognosis than EGISTs, with cumulative 5-year survival rates of 85% for GISTs and 38%-60.9% for EGISTs. Among EGISTs, omental tumors have higher overall survival than mesenteric or retroperitoneal tumors. Additionally, age of >60 years, male sex, larger tumor size, higher mitotic rate, and nuclear pleomorphism are associated with worse prognosis in EGISTs.