Value of MR imaging in differentiating benign from malignant soft-tissue masses: study of 95 lesions.

MR imaging has largely replaced CT as the technique of choice for preoperative staging of patients with soft-tissue masses. Whether MR imaging can be used to differentiate benign from malignant masses is controversial. Our experience suggests that MR imaging often can characterize soft-tissue masses accurately. To evaluate this question further, we studied 95 consecutive lesions (50 benign and 45 malignant). Consecutive cases were selected to simulate our clinical practice. Surgical proof was available for all masses except hematomas, for which clinical follow-up confirmed the diagnosis. MR images were interpreted twice by three radiologists. The first review was accomplished without any clinical history and the second review with clinical history. Reviewers were asked to classify the lesion as benign or malignant on the basis of their clinical knowledge and analysis of MR image features (size, lesion margin, signal homogeneity, and neurovascular or bone involvement). Although interpretation varied somewhat because of the experience of the reviewers, the specificity and accuracy of diagnosis averaged 90% for both benign and malignant lesions. Negative predictive value for malignancy averaged 94% among the three reviewers. MR imaging is the technique of choice for identification and characterization of soft-tissue masses. The nature of the lesion (benign vs malignant) can be determined in the majority of cases.