Gastrointestinal stromal tumors (GISTs) are the most common stromal tumors affecting the gastrointestinal tract, but still account for less than 1% of all gastrointestinal tumors. The estimated annual incidence of clinically relevant GIST is approximately 1 in 100,000 per year. Approximately 85% of GISTs contain mutually exclusive activating mutations in genes encoding the KIT proto-oncogene, receptor tyrosine kinase (KIT), or platelet-derived growth factor receptor alpha (PDGFRA) tyrosine kinase receptor, resulting in Ligand-independent activation that sensitizes tumor cells to tyrosine kinase inhibitors (TKIs).