Accuracy of MRI-based Diagnoses for Distal Upper Extremity Soft Tissue Masses.

UNLABELLED: To determine the accuracy of the pre-operative MRI-based diagnosis of soft tissue masses in the forearm, wrist, and hand, the records of 144 patients who underwent an MRI followed by excision of a soft tissue mass in the forearm, wrist, or hand were reviewed. The MRI-based diagnosis was compared to the histological diagnosis, which was considered the gold standard. The sensitivity, specificity, positive predictive value, and negative predictive value of the MRI-based diagnosis were calculated. A multivariate regression analysis was performed.While the accuracy of the MRI-based diagnosis varied widely, there was an overall sensitivity of 75 %. The most accurate diagnosis was an MRI-based diagnosis of ganglion cyst, which had a sensitivity of 94.7 % and a specificity of 94.4 %. Of particular concern was that the MRI-based diagnosis of a malignancy was only 66.7 % sensitive, with a positive predictive value of 44.4 %. On multivariate regression analysis, there was a trend towards improved accuracy in the wrist when compared to the finger, although this did not reach statistical significance.While pre-operative MRI remains a valuable tool for the evaluation of soft tissue masses in the distal upper extremity, caution is warranted when basing the diagnosis on MRI evidence alone. LEVEL OF EVIDENCE: Level IV/Diagnostic.