Level I | Tumor thrombus is either at the entry of renal vein or within the IVC < 2 cm from the confluence of renal vein and IVC. |
Level II | Tumor thrombus extends within the IVC > 2 cm above the confluence of renal vein and IVC, but still remains below the hepatic veins. |
Level III | Tumor Thrombus involves the intrahepatic IVC. |
Level IV | Tumor thrombus extends above diaphragm or into the right atrium. |