PTK2B and nonpapillary renal cell carcinoma: It binds to specific tyrosine kinase receptor, VEGF-R2, expressed on both endothelial and ccRCC cells [6], further resulting in downstream signaling which mediates the activation of Ras/MEK/ extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) pathway.