Characterization of adnexal mass lesions on MR imaging

The aim of our study was to evaluate the accuracy of MR imaging in the detection and characterization of adnexal mass lesions and to determine which imaging features are predictive of malignancy.

We prospectively performed MR imaging in 104 patients (age range, 19-87 years; mean age, 50 years) with clinically or sonographically detected complex adnexal masses. We used a 1.5-T unit to perform T1-, T2-, and fat-suppressed T1-weighted sequences before and after IV injection of gadolinium. The adnexal lesions were examined for several features including size, shape, character (solid-cystic), vegetation, signal intensity, and enhancement. Secondary signs such as ascites, peritoneal disease, and lymphadenopathy were noted. We compared the imaging features with the surgical and pathologic findings. Multiple logistic regression analysis was performed on all MR imaging features.

A total of 163 lesions--94 benign and 69 malignant lesions--were examined. On MR imaging, 95% (155/163) of the lesions were detected. The overall accuracy for the diagnosis of malignancy was 91%. On univariate analysis, the imaging features associated with malignancy were a solid-cystic lesion, irregularity, and vegetation on the wall and septum in a cystic lesion, the large size of the lesion, an early enhancement on dynamic contrast-enhanced MR images, and the presence of ascites, peritoneal disease, or adenopathy. On multiple logistic regression analysis, ascites and vegetation in a cystic lesion were the factors most significantly indicative of malignancy.

MR imaging is highly accurate in the characterization of adnexal mass lesions, and the best predictors of malignancy are vegetation in a cystic lesion and ascites.