Microvascular tumor invasion: prognostic significance in low-stage renal cell carcinoma.

OBJECTIVES: To evaluate the role of microvascular tumor invasion (MVI) in clinical behavior and prognosis of low-stage renal cell carcinoma.

METHODS: We retrospectively reviewed the records of patients who had undergone radical nephrectomy from 1990 to 2004 for clinically confined kidney tumors (Stage T1-T2N0M0) with a minimal follow-up period of 1 year. The pathology slides were reviewed regarding tumor diameter, pathologic tumor stage, histologic cell type, nuclear grade, macroscopic or MVI, perirenal fat invasion, and neoplastic lymph node involvement.

RESULTS: A total of 48 patients, 22 men and 26 women (mean +/- SD age 50.73 +/- 13.03 years, range 20-80) were included in the study. The patients were followed up for a mean +/- SD of 37.65 +/- 18.19 months (range 12-60). MVI was encountered in 8 patients (16.7%); 50% developed treatment failure in the form of distant metastases. Of the 40 patients without MVI, only 2 (5%) had treatment failure. MVI had a statistically significant association with sex (P = 0.017) and stage (P = 0.039). On comparing treatment failure with different patient and histologic parameters, a statistically significant association was noted with sex (P = 0.006) and MVI (P = 0.005). The 5-year disease-free survival rate was estimated at 45% and 90% when MVI was and was not present. Only MVI showed an independent statistically significant impact (P = 0.007) on multivariate analysis considering the impact of MVI, stage, grade, cell type, perirenal fat invasion, tumor size, and patient age on disease-free survival.

CONCLUSIONS: The results of our study have shown that MVI is an independent and relevant prognostic parameter for clinically low-stage renal cell carcinoma.