8.

Mayo Clinic tumor thrombus classification

Level of tumor thrombus	Description
Level 0	Thrombus limited to the renal vein, detected clinically or during assessment of the pathological specimen
Level I	Tumor thrombus extends into the IVC, <2 cm above the renal vein
Level II	Tumor thrombus extends into the IVC, >2 cm above the renal vein but below the hepatic veins
Level III	Tumor thrombus extends above the hepatic veins but below the diaphragm
Level IV	Tumor thrombus extends above the diaphragm.