Segmental Renal Vein Tumor Thrombus in Early-stage RCC: Intraoperative Diagnosis, Clinical Significance, and a Systematic Review with Meta-analysis

Objective: To summarize the clinical characteristics of renal cell carcinoma (RCC) patients with segmental vein tumor thrombus detected during partial nephrectomy (PN) and explore its clinical significance, so as to deepen the understanding of the pathogenesis of RCC-associated tumor thrombus. Additionally, we aim to evaluate the prognostic impact of renal vein invasion (RVI) in RCC, particularly its influence on recurrence-free survival (RFS), through a meta-analysis. Methods: A retrospective analysis was conducted on the clinical data of 209 RCC patients (162 cases of T1a stage, 47 cases of T1b stage) who underwent PN in The Second Affiliated Hospital of Xi'an Jiaotong University from September 2023 to July 2025. Among them, 8 patients were intraoperatively identified with extracapsular segmental venous tumor thrombus. in this study, “grossly visible vascular invasion (GVI)” refers to intraoperatively observed, macroscopic segmental venous tumor thrombus (ESVTT/SRVI) detected during nephron-sparing surgery, regardless of preoperative imaging findings. Intraoperative findings, pathological characteristics, and follow-up outcomes were recorded and analyzed. Furthermore, a meta-analysis of 12 studies (141,504 patients) was conducted to assess the impact of RVI on RFS, comparing it to other invasion patterns such as perinephric fat invasion (PFI). Results: Among the 8 cases of extracapsular segmental vein tumor thrombus, 1 was at T1a stage and 7 at T1b stage. Preoperative computed tomography (CT) showed round or roundish solid renal masses with heterogeneous density on non-contrast scans, significant enhancement on contrast-enhanced scans, and markedly weaker enhancement in the renal parenchymal phase compared with normal renal tissue. The average tumor diameter was (4.9±0.2) cm, with clear boundaries and no evidence of vascular invasion. Postoperative pathology confirmed pT3a clear cell carcinoma in all cases, with International Society of Urological Pathology (ISUP) grades ranging from Ⅰ to Ⅳ, and all surgical margins were negative. After surgery, 5 patients received adjuvant immunotherapy. During a median follow-up of 10.3 (3.8-22.8) months, no tumor recurrence or metastasis was observed. The meta-analysis revealed that RVI significantly increased recurrence risk, with a pooled hazard ratio (HR) of 1.76 (95% CI 1.23–2.51) for RVI compared to perinephric fat invasion (PFI), and a pooled HR of 1.85 (95% CI 1.35–2.53) compared to non-RVI patients. Furthermore, multiple patterns of vascular invasion (HR 1.60, 95% CI 1.31–1.94) and sarcomatoid differentiation (HR 2.81, 95% CI 2.12–3.72) were strongly correlated with higher recurrence risks. Conclusion: Renal cell carcinoma (RCC) has a strong tendency for vascular invasion, and this study highlights that even clinically T1 tumors can harbor glossly visible segmental venous tumor thrombus (ESVTT/GVI) detected only at surgery. In this context, ESVTT represents a macroscopic manifestation of segmental renal vein involvement along the continuum from microscopic vascular invasion to main renal vein thrombus, with potential impact on staging, choice of nephron-sparing versus radical surgery, and postoperative surveillance. Complementing these institutional observations, the meta-analysis demonstrates that renal vein invasion (RVI) is consistently associated with significantly worse recurrence-free survival (RFS), supporting the need to recognize and systematically record grossly visible segmental venous invasion as a clinically meaningful risk feature. Together, these findings justify larger multi-center and prospective efforts to standardize intraoperative documentation of GVI/ESVTT, correlate it with imaging and pathology, and ultimately refine risk stratification and treatment strategies for patients with RCC.