(1) Background: Overall survival of the patients with renal cell carcinoma (RCC) depends mostly on extra-renal extension, documented by the invasion of the pelvicalyceal system, or the perinephric/renal sinus fat or the renal vein/its segmental intraparenchymal branches. Staging may be challenging because of the high inter-observer variability. We have introduced a more accurate procedure to detect the extra-renal extension and, to possibly evaluate the impact of such more laborious approach, we have compared the RCC pathological staging obtained following both standard and modified procedures; (2) Methods: We selected 54 consecutive cases of RCC diagnosed 18 months before and 54 consecutive cases diagnosed 18 months after the introduction of the new method of sampling. Clinico-pathological characteristics have been statistically analyzed; (3) Results: Most of the features analyzed were non statistically significative, except the extra-renal invasion. More precisely, the occurrence of retrograde venous invasion was higher in the cases grossly approached with the more accurate method; (4) Conclusions: Extra-renal extension to intraparenchymal renal vein branches may be underestimated, leading to an inappropriate under-staging. Using more accurate staging procedures, to disclose the occurrence of intra-renal veins tumoral thrombosis, helps to better define the pathological stage, allowing patients to benefit of better fitting treatments.