KIT and gastrointestinal stromal tumor: Tumors expressing CD117 are susceptible to therapy with tyrosine kinase inhibitors (TKIs), such as imatinib mesylate, which is currently the basis for treatment of gastrointestinal stromal tumors (GISTs), due to the presence of underlying mutations in exons 9 and 11 of the C-KIT gene; however, such mutations have not been identified in CD117-positive renal tumors, thus undermining the efficacy of TKIs in this setting [54,56].