Resistance to blood flow in ovarian tumors: correlation between resistanceindex and histological pattern of vascularization

Objective To investigate the correlation between the histological patterns of vascularization and the resistance index (RI) in ovarian tumors. Design In a retrospective study, the histological sections of the ovarian t umors with known preoperative RI values were reviewed and the pattern of va scularization was studied. Subjects Twenty-two women underwent B-mode sonography and color Doppler ult rasound within 3 days prior to explorative laparotomy for ovarian masses in the years 1992-93. Methods The RI of the ovarian tumors was calculated as the mean of three co nsecutive waveforms with the lowest RI. The representative histological sec tions were evaluated for quantify of arterioles and venules, after staining by Masson trichrome and Elastic Van Gieson. The arteriolar fraction (defin ed as the number of arterioles divided by the sum of the arterioles plus ve nules) and the density of vessels (defined as the number of arterioles and venules per microscopic field) were calculated in each histological section and correlated with the preoperative RI values. Results The mean RI was 0.36+/-0.07 for malignant tumors and 0.57 +/- 0.03 for benign tumors. Ovaries with malignancies showed significantly lower art eriolar fraction values (0.30 +/- 0.12) than those with benign tumors (0.56 +/- 0.05) and those with metastatic tumors (0.43 +/- 0.2) (p < 0.002 and p < 0.001, respectively). The density of vessels was higher in malignant tum ors (8.0 +/- 3.8) than in benign lesions (2.7 +/- 1.5) (p < 0.01). RI value s showed a strong positive correlation (r = +0.85, p < 0.0005) with the art eriolar fraction and a negative and weaker correlation (r = -0.69, p < 0.00 1) with the density of vessels. Conclusions RI values are predominantly determined by the proportion of art erioles. The correlation between the histological pattern of vascularizatio n and RI values reflects tumor angiogenesis and increases understanding of the advantages and limitations of measuring vascular resistance by color Do ppler ultrasound.