FLT3 and renal cell carcinoma: Sunitinib (SU011248), a small molecule inhibitor of class III and class IV receptor tyrosine kinases, including VEGFR1-3, PDGFR-α/β, c-Kit, Flt3, and RET, is currently approved for the treatment of renal cell carcinoma (RCC) and imatinib-refractory gastrointestinal stromal tumors (GIST) [12,13].