LAUSR

Renal cell carcinoma (RCC) is the most common type of malignant mass found in the kidney. It demonstrates well-described and relatively predictable patterns of growth and extra-renal spread – all of which are used for clinical staging of the disease. While invasion of surrounding tissue is not uncommonly seen, RCC is also known to form tumor thromboses within the renal vein and the inferior vena cava (IVC). Thrombotic spread within the lumen of the collecting system and the proximal ureters, however, is a rare event that has seldom been described in the literature and has not been studied in the context of tumor staging. We present the case of a 79-year-old male who presented with a large renal mass on imaging suspicious for RCC. Upon postoperative histopathological analysis, RCC was confirmed and thrombotic spread of tumor within the renal pelvis and into the proximal ureter was discovered.