Inverse correlation of microvessel density with metastasis and prognosis in renal cell carcinoma

Background: Although a correlation between microvessel density (MVD) and tumor aggressiveness has been established for several malignancies, the data for renal cell carcinoma (RCC) is conflicting. In order to clarify the significance of MVD, we investigated the relationships between MVD and tumor stage, grade, size, occurrence of metastasis and patient survival. Methods: Tumor specimens from 70 patients with primary renal cell carcinoma were examined by immunohistochemical staining for CD34. Results: There was a tendency for MVD to decrease from G1 to G3 tumors or from stage T1 to T3 tumors, although this was not statistically significant. However, the MVD for 56 non-metastatic and 14 metastatic tumors were significantly different (P = 0.005) at 109 +/- 67 and 58 +/- 35 per x400 field (mean +/- SD), respectively. Microvessel density for 36 large and 34 small tumors was also significantly different (P < 0.0001) at 48 +/- 22 and 142 +/- 54 per x400 field, respectively. The survival rate of patients with small, low grade and hypervascular tumors was significantly higher than that of patients with large (P = 0.0015), high grade (P = 0.05) or low MVD (P = 0.039) tumors. Cox proportional hazards regression analysis showed that tumor grade and size emerged as independent prognostic factors. Conclusion: High MVD in RCC was inversely associated with tumor aggressiveness, but MVD was not the independent prognostic factor.