This case illustrates a T3a renal tumor extending into the left renal vein. If tumor extended into the IVC it would be T3b and if it extended into the IVC above the diaphragm it would be T3c. T3a tumor classification also includes tumors that invade peri-renal fascia and renal sinus fat 1.
It also demonstrated normal venous anatomy by obstructing the left gonadal vein as it drain drains directly into the left renal vein whereas the right gonadal vein usually, as in this case, drains into the IVC. This explains the ultrasound teaching that the kidneys should be imaged especially if you detect a unilateral left varicocele on testicular ultrasound.