Mutational analysis of c-KIT and PDGFRA receptors in gastrointestinal stromal tumours

Abstract

Introduction: The pathogenesis of gastrointestinal stromal tumors (GISTs) is generally associated with activating mutations of the proto-oncogene tyrosine-protein kinase Kit (c-KIT). However, about 15% of GISTs do not harbour c-KIT mutations. It is estimated that 5% of these GISTs have mutations in the platelet-derived growth factor receptor α (PDGFRA). Accurate diagnosis of GIST has become very important since the availability of targeted therapy with tyrosine kinase inhibitors, such as imatinib mesylate. The routine workup for GIST diagnosis includes immunohistochemistry for CD117 (c-KIT polyclonal antibody), as it is estimated that 95% of GIST cases show positive immunoreactivity. However, it can be observed that the routinely used immunohistochemical analysis does not provide complete sensitivity for GIST diagnosis, as there are nearly 5% of GISTs that are negative for c-KIT immunohistochemistry. Mutational analysis for c-KIT and PDGFRA can confirm the diagnosis of GIST, particularly in CD117-negative suspect GIST. Moreover, specific mutations have a prognostic and/or a predictive value for response to therapy.