Gastrointestinal stromal tumours (GISTs) are rare mesenchymal malignancies of the gastrointestinal (GI) tract that are a distinct disease entity based on their molecular pathogenesis, immunohistochemical staining, and responsiveness to targeted therapy. The annual incidence of GIST is 11 to 15 cases per million in studies based on Caucasian populations, with GISTs detected at autopsy and those with a low malignancy potential included. GISTs vary in malignant potential ranging from small, incidentally detected turnours with excellent outcome, to aggressive sarcomas. The appearance and behaviour of GISTs can differ depending on the location within regions of the GI tract. Approximately one third of GISTs worldwide are in the high-risk category for malignant potential, and an inverse correlation between level of risk and survival of GIST patients has been observed. KIT, or more rarely PDGFRA, gene mutations are key to GIST oncogenesis. Criteria for identification of GIST, based on immunoreactivity for the CD117 epitope expressed on KIT, have improved the accuracy of GIST diagnosis and contributed to recognition of GIST as a distinct disease entity. Other markers for diagnostic specificity for GIST are under consideration. Improved diagnosis has led to a slight increase in the observed incidence rate of GIST, which has stabilised in recent years. GISTs are refractory to conventional chemotherapy and surgery was the most effective therapy for GIST prior to the development of the targeted therapy imatinib. Although surgery remains first-line therapy for primary GIST, imatinib is indicated as frontline therapy for metastatic or unresectable GIST.
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