Widely used modification of Flocks-Kadesky staging system to describe renal cell carcinoma. Stage 1, confined to parenchyma; stage 2, involvement of perinephric fat and/or adrenal but still confined to Gerota fascia; stage 3a, involvement of main renal vein or vena cava but no spread to regional lymph nodes; stage 3b, involvement of regional lymph nodes but no involvement of venous structures; stage 3c, involvement of regional lymph nodes and venous structures; stage 4a, involvement of acfiacent organs; stage 4b, distant metastases.