Summary
Gastrointestinal stromal tumours (GISTs) are defined as gastrointestinal mesenchymal tumours expressing a protooncogene protein called CD117, which is detected by immunohistochemistry. GISTs are rare and constitute about 1-3% of all gastrointestinal (GI) malignancies, nevertheless, they are the commonest type of GI mesenchymal tumours. Data concerning the worldwide prevalence of GISTs are lacking. Data from population based studies in Finland suggested an annual incidence of all GISTs of around 10-20 per million. Annual incidences of 6.8 cases per million and 14.5 per million were estimated for the USA and in western Sweden, respectively, with a slight predominance among men. GISTs differ from gastrointestinal smooth muscle and neural tumours. Clinical features depend on the size and site of the tumour and include acute or chronic bleeding, intestinal obstruction, perforation, alteration of bowel habits, vague abdominal discomfort, dysphagia and an externally palpable abdominal mass. It is now believed that GISTs originate from gastrointestinal pacemaker cells known as the interstitial cells of Cajal, which control gut motility, or from a precursor of these cells. Many GISTs contain mutations in the c-kit (KIT) protooncogene coding for c-KIT (CD117). Most of these mutations are found in exon 11 and to a lesser extent in exons 9, 13 or 17. Some GISTs carry a mutation in the platelet-derived growth factor receptor-alpha (PDGFRA) gene. To implement therapy, it is important to diagnose GISTs accurately and distinguish them from other gastrointestinal mesenchymal tumours. Complete surgical excision is the treatment of choice for localised GISTs. The role of radiotherapy is limited by the potential toxicity to surrounding structures. The discovery of the antitumour effects of the molecular inhibitor imatinib mesylate in metastatic and inoperable GISTs, was a remarkable breakthrough. *Authors: Prof. M. V. Chandu de Silva and Dr R. Reid (February 2005)*.
