Fig. 1

The Mayo classification of macroscopic venous invasion in RCC. Level I: The tumor thrombus is either at the entry of the renal vein or within the IVC < 2 cm from the confluence of the renal vein and the IVC. Level II: The thrombus extends within the IVC > 2 cm above the confluence of the renal vein and the IVC but still remains below the hepatic veins. Level III: The thrombus involves the intrahepatic IVC. The size of the thrombus ranges from a narrow tail that extends into the IVC to one that fills the lumen and enlarges the IVC. Level IV: The thrombus extends above the diaphragm or into the right atrium