Gastrointestinal Stromal Tumors in the 21<sup>st</sup> Century

Abstract

Gastrointestinal stromal tumours (GISTs) are rare mesenchymal lesions accounting for only 0.2% of all gastrointestinal neoplasms. These tumors arise from the interstitial cells of Cajal, with mutations described in proto-oncogenes such as KIT, PDGFRA, DOG-1, and SDH. The majority of these lesions are asymptomatic, thus the true incidence remains unknown. While patients typically undergo initial endoscopy, CT scan and/or MRI, findings are often nonspecific and require a biopsy to identify the tumor. As such, immunohistochemical evaluation is the gold-standard for the accurate diagnosis of GIST. Though surgical excision remains the gold-standard for curative management, the discovery of imatinib, a tyrosine kinase inhibitor (TKI), has revolutionized the treatment of GIST in the 21st century as a “prototype” of molecular targeted therapy for solid tumors. Risk assessment for recurrence divides these tumors into low and high-risk categories. In the latter, a role for adjuvant therapy with TKI confers a significantly better prognosis than previously observed. However, secondary mutations conferring drug resistance remain an ongoing challenge for management, as few alternative treatment options are available for patients intolerant/refractory to TKI therapy. In this review, we summarize the epidemiology, molecular pathogenesis, clinical presentation, diagnosis, pathology features, management options, and prognostic features of GISTs.