Background: To clarify the differences in angiogenesis between benign and malignant ovarian tumors, the authors examined the immunohistochemical characteristics and the density of tumor vessels in both tumor groups. Intratumoral vascularization was observed preoperatively by transvaginal color Doppler ultrasound.
Methods: The authors examined 106 patients with ovarian tumors preoperatively for the presence or absence of intratumoral blood flow and evaluated the blood flow waveforms of tumor vessels in patients showing intratumoral vascularization, using a resistance index (RI). The characteristics of both smooth muscle and endothelial cells in the vessels of each tumor were immunohistochemically assessed, using monoclonal antibodies against smooth muscle actin (SMA) and CD34 (an endothelial cell marker). The microvessel density (MVD) identified by CD34 was also evaluated in each tumor.
Results: Intratumoral blood flow was found in 64 of 106 patients (60.4%). The tumors in 44 of these 64 patients were histopathologically benign, and the tumors in 20 were malignant. The malignant tumors showed a low RI (mean, 0.39 +/- 0.09) compared with benign tumors (mean, 0.62 +/- 0.12) (P < 0.001). The vessels of malignant tumors significantly demonstrated poor SMA expression and intense CD34 expression compared with the vessels of benign tumors. However, no significant differences were observed in MVD between the benign and malignant tumors.
Conclusions: In this study, immunohistochemical analysis demonstrated that low resistance to blood flow in vessels within malignant ovarian tumors may be associated with a poorly developed muscular coat in the tumor vessels, compared with that observed in benign tumors. The difference in the angiogenic natures of benign and malignant ovarian tumors showing intratumoral blood flow may thus be correlated with the endothelial cell activity of the tumor vessels and not the MVD.