Increased microvascular density predicts relapse in Wilms' tumor

Background/Purpose: Tumor stage and histology are the most important prognostic criteria in Wilms' tumors; however, a subset of patients remains who have favorable histology tumors and unexpectedly relapse. The authors postulated that increased microvascular density (MVD), a hallmark for angiogenesis, could identify patients at risk for relapse. Methods: A case-control study was used to compare relapse (n = 15) with nonrelapse tumors (n = 35). Tumor MVD was counted in 5 random high-powered fields (hpf) using anti-Factor VIII antibody and expressed as mean vessel count/hpf +/- SEM. MVD and clinical data were evaluated using univariate analysis and student's t test. Results: The relapse group had higher MVD than the nonrelapse group (34.9 +/- 2.9 v 22.4 +/- 2; P < .05). When evaluating the favorable histology (FH) group alone, there was higher MVD in the relapse group (32.4 +/- 2.7 v 19 +/-1.8; P < .05). MVD was found to be the only predictor of relapse when compared with age, sex, tumor weight, and histology. Conclusions: These results suggest that increased MVD can identify Wilms' tumor patients at high risk for relapse, especially those patients with favorable histology tumors. A larger study is warranted to determine the potential utility of MVD in stratification of Wilms' tumor patients.