Background/Purpose:Intratumoral angiogenesis quantified by microvessel densit y(MVD)has been shown to be a strong prognostic indicator in a number of malign ant tumors.Its association with prognosis in Ewing sarcoma has not been previou sly studied.The aim of our study was to investigate the relationship between an giogenesis and clinical outcome in Ewing sarcoma.Methods:Twenty-seven patient s with Ewing sarcomawere included in a retrospective immunohistochemical study.Sections from diagnostic biopsies were immunostained using anti-von Willebrand factor antibody and microvessels were counted at 400×magnification on three mic roscopic fields per patient.Microvessel density was correlated with overall and disease-free survival as a continuous variable using univariate regression ana lysis and as a dichotomous variable by Kaplan-Meier and log-rank analysis.Cor relation between clinicopathologic variables and the degree of angiogenesis was tested using χ2 test.Results:Increasing MVD was not con-firmed to be a poor prognostic factor in univariate analysis.Also,statistically significant differ ence was not found in overall survival or disease-free survival between patient s with high(> 31.6 vessels per field)and low(≤31.6 vessels per field)micro vessel counts.Finally,there was no difference regarding the metastatic rate be tween patients with high and low microvessel counts.Conclusions:Our results di d not confirm increasing angiogenesis quantified by MVD to be predictive of prognosis or pulmonary metastasis in Ewi ng sarcoma.The diffuse pattern of distribution of microvessels found in Ewing s arcoma may be responsible for the observed lack of prognostic significance of an giogenesis.Future work is required to assess the prognostic importance of MVD i n this disease. Background/Purpose:Intratumoral angiogenesis quantified by microvessel densit y(MVD)has been shown to be a strong prognostic indicator in a number of malign ant tumors.Its association with prognosis in Ewing sarcoma has not been previou sly studied.The aim of our study Was to investigate the relationship between an giogenesis and clinical outcome in Ewing sarcoma.Methods:Twenty-seven patient s with Ewing sarcomawere included in a retrospective immunohistochemical study.Sections from diagnostic biopsies were immunostained using anti-von Willebrand factor antibody and microvessels were counted at 400×magnification on three mic roscopic fields per patient.Microvessel density was correlated with overall and disease-free survival as a continuous variable using univariate regression ana lysis and as a dichotomous variable by Kaplan-Meier and log-rank analysis.Cor relation between clinicopathologic Variables and the degree of angiogenesis was tested using χ2 test.Results:Increasing MVD was Not con-firmed to be a poor prognostic factor in univariate analysis.Also, statistically significant difference ence was not found in overall survival or disease-free survival between patient s with high (> 31.6 vessels per field) and low (≤31.6 vessels per Field)micro vessel counts.Finally,the was was no difference regarding the metastatic rate be tween patients with high and low microvessel counts.Conclusions:Our results di d not confirm increasing angiogenesis quantified by MVD to be predictive of prognosis or pulmonary metastasis in Ewi ng sarcoma.The diffuse pattern of distribution of microvessels found in Ewing s arcoma may be responsible for the observed lack of prognostic significance of an giogenesis.Future work is required to assess the prognostic importance of MVD in this disease.